Magnetic compass confirmation for avoidance of interference in wireless communications

ABSTRACT

In one embodiment, a process obtains a first compensated directional reading from a first directional sensor of a directionally sensitive system, and obtains a second compensated directional reading from a second directional sensor of the directionally sensitive system. The process may then determine, a difference between the first compensated directional reading and the second compensated directional reading, and declares, in response to the difference being greater than an acceptable threshold, an inaccurate directional reading. As such, the process may then prevent performance of a directionally sensitive action by the directionally sensitive system in response to an inaccurate directional reading.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/379,023 filed on Dec. 14, 2016, entitled AVOIDANCE OFINTERFERENCE IN WIRELESS COMMUNICATIONS, by Reis, et al., which claimspriority to U.S. Provisional Patent Appl. No. 62/267,065 filed on Dec.14, 2015, entitled CHANNEL CLEARANCE AND AVOIDANCE IN WIRELESSCOMMUNICATIONS, by Reis, et al., the contents of each of which beingincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to wireless communicationsystems, and, more particularly, to magnetic compass confirmation foravoidance of interference in wireless communications.

BACKGROUND

Wireless communication systems have become ubiquitous in the worldtoday, such as, for example, cellular mobile telephony, point-to-pointmicrowave systems, satellite communication systems, and so on. Withineach of these systems, and particularly due to the co-existence of suchsystems, challenges are presented when it comes to managingcommunication in a manner that prevents or at least minimizesinterference. Common methods of interference minimization and/oravoidance may include use of different frequency bands, differentpolarizations, multiplexing techniques, geographical separation, etc.These methods typically work well for networks having fixed transmittersand receivers. When receivers or transmitters are allowed to move,however, the occurrence of interference may be greater, and performancemay degrade.

For example, certain wireless communication frequencies (e.g., C-bandcommunications) can only communication when there is a clearline-of-sight (LOS) between transmitter and receiver. Accordingly,interference of a C-band transmitter with a C-band receiver is possibleonly if there is a clear line-of-sight from the transmitter to thereceiver. As such, if the transmitter roams, it may move from a point atwhich no interference was possible to one in which it becomes apotential interferer with the receiver. Other factors involved indetermining whether a transmitter, in general, interferes significantlywith a received signal, in addition to overlapping communicationbands/channels, may further include transmit power, receive antennatype/gain, polarizations, distance from the transmitter to the receiver,and so on.

In certain environments, radio signal interference may be nothing morethan a slight nuisance, while in other environments, the interferencemay be more problematic to the communication network, such as reducedbandwidth, lost (e.g., and repeated) messages, and so on. In still otherenvironments, however, such interference may not only be particularlydetrimental (e.g., introducing noise to received voice communication orpartial/complete loss of picture for TV communication), but it may alsobe strictly prohibited by communication regulations, perhaps even beingcriminally offensive. Regardless of the environment, it is thusbeneficial to ensure adequate interference mitigation, and in someinstances absolute interference avoidance.

SUMMARY

According to one or more of the embodiments herein, a process obtains afirst compensated directional reading from a first directional sensor ofa directionally sensitive system, and obtains a second compensateddirectional reading from a second directional sensor of thedirectionally sensitive system. The process may then determine, adifference between the first compensated directional reading and thesecond compensated directional reading, and declares, in response to thedifference being greater than an acceptable threshold, an inaccuratedirectional reading. As such, the process may then prevent performanceof a directionally sensitive action by the directionally sensitivesystem in response to an inaccurate directional reading.

Various specific embodiments are described in detail below, such astypes and arrangements of sensors, various directionally sensitiveactions, and so on, and the summary is not meant to be limiting to thepresent disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments herein may be better understood by referring to thefollowing description in conjunction with the accompanying drawings inwhich like reference numerals indicate identically or functionallysimilar elements, of which:

FIG. 1 illustrates an example communications network;

FIG. 2 illustrates an example of communication interference;

FIG. 3 illustrates an example point-to-point communications network withthe potential for interference from a satellite communications network;

FIG. 4 illustrates an example satellite communications network;

FIG. 5 illustrates an example device configuration, e.g., as a server;

FIG. 6 illustrates another example device configuration, e.g., as aterminal;

FIG. 7 illustrates an example antenna configuration table;

FIGS. 8A-8B illustrate an example of antenna patterns;

FIG. 9 illustrates an example of antenna gain patterns;

FIGS. 10A-10B illustrate example demonstrations of link margin, linkbudget, and noise floors in wireless communications;

FIG. 11 illustrates an example of line-of-sight communication;

FIGS. 12A-12B illustrate an example simplified procedure for avoidinginterference in wireless communications according to one exampleembodiment herein;

FIG. 13 illustrates an example receiver acceptance cone;

FIG. 14 illustrates an example receiver protection zone (simplified);

FIG. 15 illustrates a simplified example of antenna lobes from anantenna site;

FIG. 16 illustrates an example gain pattern for an example (e.g.,2-meter) point-to-point microwave dish;

FIG. 17 illustrates an example polygon resulting from link budgetcalculation towards a receiver, representing a noise floor crossingboundary for a given transmission configuration from surroundinggeographical locations;

FIG. 18 illustrates an example of intended receiver diversity andazimuth angles due to such diversity;

FIG. 19 illustrates an example of how a smearing operation may affect aprotection zone to compensate for any potential inaccuracy by expandingit in certain directions;

FIG. 20 illustrates an example cut-away view of an illustrativeterrain/topology along a line from an incumbent receiver to pointswithin its example protection zone;

FIG. 21 illustrates an example reduced protection zone due to topologyand line-of-sight considerations;

FIG. 22 illustrates an example of major and minor horizons associatedwith the reduced protection zone of FIG. 21;

FIGS. 23A-23B illustrate a geo-locational example of avoidinginterference in wireless communications in accordance with thetechniques herein;

FIGS. 24A-24B illustrates an example of choosing satellite diversity foravoiding interference in wireless communications in accordance with thetechniques herein;

FIG. 25A illustrates an example of active point-to-point microwave linksbetween 5925.01 MHz and 5930.0 MHz in the United States;

FIG. 25B illustrates an example of a difference between northerly facingand southerly facing protection zones;

FIGS. 26A-26B illustrate examples of a directionally sensitive systemhaving multiple directional sensors;

FIGS. 27A-27B illustrate an example of how magnetic interference canaffect directional sensors differently;

FIGS. 28A-28B illustrate an example of how antenna misdirection canaffect avoidance of interference in wireless communication;

FIGS. 29A-29B illustrate an example of how misdirection can affect agraphical user interface (GUI) for use with avoidance of interference inwireless communication; and

FIG. 30 illustrates an example procedure for magnetic compassconfirmation, e.g., for avoidance of interference in wirelesscommunications in accordance with one or more embodiments describedherein.

DESCRIPTION OF EXAMPLE EMBODIMENTS

A communication network is a distributed collection of nodes (e.g.,transmitters, receivers, transceivers, etc.) interconnected bycommunication links and segments for transporting signals or databetween the nodes, such as telephony, TV/video, personal computers,workstations, mobile devices, servers, routers, base stations,satellites, or other devices. Many types of communication networks areavailable, including, but not limited to, computer networks (e.g., localarea networks, wide area networks, and so on), communication networks(e.g., cellular networks, broadband networks, etc.), infrastructure orbackhaul networks (e.g., C-Band/microwave inter-tower or“point-to-point” (PtP) networks, etc.), and many others.

FIG. 1 illustrates an example, and simplified, communications network100. As shown, one or more individual networks 104 may contain variousdevices 110 communicating over links 120 specific to the particularnetwork 104, or else between networks. As will be appreciated, networks104 may include, but are not limited to, local area networks (LANs),wide area networks (WANs), the Internet, cellular networks, infrarednetworks, microwave networks, satellite networks, or any other form orcombination of data network configured to convey data betweencommunicating devices. Networks 104 may include any number of wired orwireless links between the devices, though, as noted herein, theinterference techniques herein are generally concerned only with thewireless (or other shared media) links. Example wireless links,therefore, may specifically include, but are not limited to, radiotransmission links, near-field-based links, Wi-Fi links, satellitelinks, cellular links, infrared links, microwave links, optical(light/laser-based) links, combinations thereof, or the like.

Data transmissions 108 (e.g., packets, frames, messages, transmissionsignals, voice/video/TV/radio signals, etc.) may be exchanged among thenodes/devices of the computer network 100 using predefined communicationprotocols where appropriate, and such communication may notably bebidirectional or unidirectional. In this context, a protocol consists ofa set of rules defining how the nodes interact with each other.

Devices 110 may be any form of electronic device operable to communicatevia networks 104. For example, devices 110 may be a desktop computer, alaptop computer, a tablet device, a phone, a smartphone, a wearableelectronic device (e.g., a smart watch), a smart television, a set-topdevice for a television, a specifically designed communication terminal,a satellite phone, a workstation, a sensor/actuator, other IoT devices,etc.

As mentioned above, wireless communication systems, particularly theco-existence of overlapping wireless communication systems, presentchallenges with regard to preventing or minimizing interference, aproblem that is exacerbated when receivers or transmitters are allowedto move. In particular, as described below, the challenge of preventinginterference is paramount when an existing communication system operateswithin dedicated frequency bands, and then a mobile transmitter for adifferent communication system is introduced into the incumbent system'senvironment that reuses those same frequency bands that the incumbentsystem may be already using.

FIG. 2 illustrates a simplified example of communication interference ina network 200. Specifically, assume that transmitter Tx-1 communicateswith a receiver Rx-1 (signals 210), and transmitter Tx-2 communicateswith a receiver Rx-2 (signals 220). In the simple event that these twopairs communicate on the same (or similar) frequency, when transmitterTx-1 attempts to transmit a signal 210 to receiver Rx-1, it mayinadvertently interfere with the ability of receiver RX-2 to receivesignals 220 from e.g., transmitter Tx-2. In other words, the interferingsignal 210 has introduced “noise” into the receiver Rx-2, interferingwith the reception of the signal 220 for which receiver Rx-2 wasintended to receive, rending the intended signal 220 indecipherable.

Notably, and as further noted above, while radio signal interference incertain environments is nothing more than a nuisance (added noise tovoice communication, messages are low priority, can be repeated, etc.),other environments may consider interference to be particularlydetrimental or even strictly prohibited. One such example network thatwould require adequate interference mitigation, and in particularabsolute interference avoidance, is the large existing incumbentcommunication system using the C-Band (5925-6425 MHz) for high-bandwidthbackhaul tower-to-tower communication. For instance, this communicationsystem utilizes a microwave transmission infrastructure that includesnumerous terrestrial receivers (or receivers, transceivers, repeaters,etc.) which are on what is generally referred to by the art as aPoint-to-Point (PtP) network with PtP Transmitters (PtPTs) transmittingmessages to respective PtP Receivers (PtPRs).

FIG. 3 illustrates an example PtP communications network 300 with thepotential for interference, for example, from a satellite communicationsnetwork 400. In particular, PtPTs 305 and PtPRs 310 may be distributedgeographically, such as on towers at the tops of mountains, buildings,etc., where PtPTs are configured to communicate wireless transmissions320 (e.g., microwave, C-band, etc.) with a respective (and opposing)PtPR, as generally indicated by the sub-text “a”, “b”, and “c”. (Notethat only receivers are subject to interference, so many referencesbelow are made to PtPRs 310 only. However, in certain embodiments,particularly for bidirectional communication systems, a receiver or PtPRmay also be a transmitter or PtPT. As used herein, therefore, the term“PtPR” may be used to describe both receivers and transmitters, whereappropriate.) In accordance with yet another embodiment, the PtPR may bean unintended satellite in the vicinity of (e.g., in angular proximityof) an intended satellite (e.g., 420, below), where transmissionintended to be received by the intended satellite may interfere with theoperations of the unintended satellite.

The PtPTs 305 and PtPRs 310 of the network (“incumbent system”,“existing system”, etc.) 300 are illustratively static; their location,antenna height above ground, direction they are pointing (azimuth andelevation), as well as their radcharacteristic (e.g., frequency, lobeshape, and polarity: horizontal, vertical, or both) are generally wellknown. According to the United States Federal Communications Commission(FCC), for instance, point-to-point microwave transmitters and receiversin the United States are registered within a Universal License Service(ULS) database, which includes details on geo-coordinates (location),antenna types, frequency bands used within the C-band, polarizations,power, etc. Currently, in the US, there are approximately 56,000 PtPRsin the C-band frequency range; all of which are operating within FCCregulations.

In order to introduce a new communication device/terminal 410 that isconfigured to transmit in the C-band within the environment 300 of theincumbent PtPRs, mechanisms need to be defined to prevent interferingwith the operations of the incumbent system. For instance, to create anetwork of earth station terminals 410 for use with C-band operationswith satellites 420 that can provide communication functionality suchas, e.g., consumer-based text messaging/light email, voicecommunication, picture/video communication, and Internet of Things(“IoT”) communications, particularly in areas unserved by terrestrialcommercial mobile radio services (“CMRS”) networks (e.g., cellular orother terrestrial mobile network coverage), such new terminals must becontrolled within the environment of the incumbent PtPRs in a mannerthat prevents harmful interference with the operations (e.g., licensedcommunication operations) of the incumbent system 300.

The techniques herein provide a robust interference protection regime toensure that prospective transmitters of one system (e.g., a satellitecommunication network 400) will not cause harmful interference to anincumbent system (e.g., PtP operations in system 300). As explainedbelow, each receiver (e.g., PtPR) will have one or more associated“Protection Zones”, where potential transmitters (e.g., earth stationterminals, UAVs, etc.) will be subject to heightened interferenceprotection requirements to ensure that no harmful interference inflictedupon a receiver (which, as described herein, may be based on sufficientavailability of frequency bands, spatial, and satellite diversity atC-band frequencies). (As described below, each incumbent receiver mayhave as many protection zones as the number of intendedreceivers/satellites that the terminal may attempt to communicate withfrom a given place, as well as different zones for other reasons, asdetailed further herein.)

FIG. 4 illustrates an example simplified satellite communicationsnetwork 400, where one or more communication transmitters 410, which maybe mobile or fixed, may be a standalone device, or may be attached to orotherwise associated with another computing device, such as a smartphone415 or other suitable cooperative device (e.g., laptop, tablet, personalcomputer, measurement sensors, other types of IoT devices, etc.).Illustratively, the transmitters 410 may be referred to herein astransmitters, terminals, mobile earth terminals (METs), prospectivetransmitters, etc. According to the illustrative satellite embodiment,the terminals 410 may communicate bi-directionally with conventional(e.g., C-band) geostationary satellites 420, which generally have aknown and static location above the earth. (Other, more complexalgorithms may be used for determining the location of, andcommunicating with, non-geostationary satellites, but for simplicity thedescription herein is based on geostationary satellites. However, theembodiments herein are not so limited.) A ground station or gateway 430(or “ground receiver”, “ground station receiver”, etc.) is anillustrative facility at the other end of the satellite transmission.The ground station 430 may include various computing servers connectedto a satellite antenna (e.g., satellite dish 435) pointing at thesatellite 420.

Transmissions 405 from the terminal 410 to the satellite are relayedfrom the satellite 420 to the dish 435 on the ground of the groundstation 430. Similarly, the ground station 430 transmits to the terminal410 by sending radio signals via its dish 435, which transmits it to thesatellite 420, which then frequency shifts this radio signal andbroadcasts it downwards to be received by the terminal 410 (notablywithin a proper link budget). As referenced herein, the “forward-path”or “downlink” refers to a frequency band that the satellite 420 uses totransmit to the terminals 410 and ground station 430. Conversely, the“return-path” or “uplink” frequency refers to a frequency band that theterminals and ground station use to transmit to the satellite. (Notethat the same or different antennas may be used by the variouscommunication devices, e.g., one for uplink, one for downlink, or onefor both, and the view and description herein is merely a simplifiedexample for purposes of illustration.) It should be noted that in theillustrative embodiment, the return-path (uplink) frequency band used bythe terminals 410 may overlap with frequency bands used by the PtPRs,and as such would be subject to PtPR interference avoidancerequirements.

Furthermore, in the illustrative embodiment, three example real-worldsatellites may be used, such as the Galaxy 3-C satellite at 95.05° W.L.,Galaxy 12 satellite at 129° W.L., and Galaxy 19 satellite at 97° W.L.Each of these three Galaxy satellites 420 currently communicate with oneof three gateway/remote control earth stations 430 in Napa, Calif. (CallSign E970391), and Hagerstown, Md. (Call Signs E050048 and E050049), andoperate on C-band frequencies in the 3700-4200 MHz(downlink/space-to-Earth) and 5925-6425 MHz (uplink/Earth-to-space)bands. Notably, any satellites, satellite systems, communicationfrequencies, ground stations, etc., may be used in accordance with thetechniques herein, and those mentioned herein are merely for use as anexample implementation of an illustrative embodiment, and are not meantto be limiting to the scope of the present disclosure.

Additionally, though specific implementation embodiments are shownherein with relation to terminals 410 being part of, or associated with,a personal communication device (e.g., for text messaging, short emails,voice communication, etc. from a phone), any number of implementationsuse the techniques described herein, such as being used for sensors oractuators (e.g., IoT implementations), vehicular control (e.g., drones,robots, unmanned aerial vehicles or “UAVs”, etc.), or any other systemthat uses wireless communication, whether located on land, a waterway(e.g., ocean), or in the air.

With reference still to FIG. 4, satellite communication network mayfurther include one or more routers 440 that may be interconnect thedevices, such as terminals 410 (and/or phones 415), gateways/groundstations 430, etc. Routers 440 may be interconnected with such devicesover standard communications links, such as cellular, internet, and soon, and may allow further communication by the devices to one or moreservers 450, which illustrative have access to one or more databases 460as described herein (e.g., the FCC ULS database). One or moreapplications, such as a visualizer tool 470, may also be available viathe servers 450 or optionally on the localized terminals 410 (e.g.,phones 415), for use as described below. Those skilled in the art willappreciate that any number of communication links, routers, devices,etc. may be available within the satellite communication network 400,and the simplified view shown herein is for illustrative purposes only.Also, while certain devices are shown separately, various functionality(processing, storage, communication, etc.) may be implemented in anysuitable configurations, such as the servers 450 being part of thegateway 430, the database 460 being part of the servers 450, and so on.Accordingly, the view in FIG. 4 and the associated description is meantas an example, and not meant to limit the scope of the presentdisclosure.

FIG. 5 illustrates a schematic block diagram of an example computingdevice 500, that may be used with one or more embodiments describedherein, e.g., as a ground station/gateway 430, server 450, or other“centralized” device. The device may comprise one or more networkinterfaces 510 (e.g., wired, wireless, etc.), at least one processor520, and a memory 540 interconnected by a system bus 550. The networkinterface(s) 510 contain the mechanical, electrical, and signalingcircuitry for communicating data to network(s) 104 and, moreparticularly, devices 410, 415, 430, etc. The network interfaces may beconfigured to transmit and/or receive data using a variety of differentcommunication protocols. Note, further, that the nodes/devices may havetwo different types of network connections 510, e.g., wireless, optical,and wired/physical connections, including connectivity to a satellitedish 435, and that the view herein is merely for illustration.

The memory 540 comprises a plurality of storage locations that areaddressable by the processor 520 for storing software programs and datastructures associated with the embodiments described herein. Theprocessor 520 may comprise hardware elements or hardware logic adaptedto execute the software programs and manipulate the data structures 545.An operating system 542, portions of which is typically resident inmemory 540 and executed by the processor, functionally organizes thedevice by, among other things, invoking operations in support ofsoftware processes and/or services executing on the device. Thesesoftware processes and/or services may illustratively include serverdatabase services 544 (e.g., controlling server database 543, and/oraccessing an external database 460), a server visualizer process 546(e.g., an app or an interface to an external visualizer tool 470), and aserver interference avoidance process 548, each as described herein.

Additionally, FIG. 6 illustrates another example device configuration600, particularly as a terminal/transmitter 410. Note that the terminal410 may be embodied as a number of various implementations, such as asmartphone peripheral attachment, a component of a smartphone, astandalone handheld device, a sensor components, IoT, vehicular (e.g.,unmanned) components, and so on. For instance, terminal 410 may be anattachment to a mobile phone 415 or other mobile device, where some ofthe processing occurs on the mobile phone and other portions, such assatellite communication, are performed on the attached (or associated)terminal 410. In accordance with another embodiment, an attachment thatcontains the terminal circuitry is loosely coupled to a mobile device.In accordance with yet another embodiment, all of the components of theterminal 410 are integrated into a single embedded (standalone) system.As such, the schematic block diagram of the device 600 is merely meantas an example representation of illustrative components representing aterminal 410 that may communicate within its own network 400 (e.g.,satellite system), while being controlled to prevent interference withinshared frequency bands of incumbent network 300.

Device 600, a terminal 410 (e.g., transmitting device), may comprise oneor more network interfaces 610 (e.g., wired, wireless, etc.), at leastone processor 620, and a memory 640 interconnected by a system bus 650.The network interface(s) 610 contain the mechanical, electrical, andsignaling circuitry for communicating data to network(s), such as anattached (or otherwise associated) mobile device (e.g., phone) 415 orother associated device, as well as other network communicationtechniques, such as wired connection to a personal computer or laptop(e.g., a USB connection). One of the network interfaces 610, inparticular, is a wireless network interface (e.g., atransmitter/receiver) configured to interface with a local antenna 660of the device, which, illustratively, may be a C-band antenna (e.g.,configured to communicate with a satellite 420, as described below), andmay comprise various communication front-end components such asamplifiers, filters, digital-to-analog and/or analog-to-digitalconverters, digital signal processors (DSPs), etc. As mentioned above,network interfaces may be configured to transmit and/or receive datausing a variety of different communication protocols, and the device 600may have different types of network connections, e.g., at least onewireless connection, but also optionally other wireless connections andwired/physical connections, and that the view herein is merely forillustration.

A memory 640 comprises the storage locations that are addressable by theprocessor 620 for storing software programs and data structuresassociated with the embodiments described herein, where the processor620 may comprise hardware elements or hardware logic adapted to executethe software programs and manipulate the data structures 645. Anoperating system 642, portions of which is typically resident in memory640 and executed by the processor, functionally organizes the device by,among other things, invoking operations in support of software processesand/or services executing on the device. These software processes and/orservices may illustratively include local database services 644 (e.g.,maintaining local database 643 itself, or accessing an externaldatabase), a local visualizer process 646 (e.g., an app or an interfaceto an external visualizer tool 470), and a local interference avoidanceprocess 648, each as described herein. Note that in certain embodiments,the terminal device 600 (410) may have limited resources (CPU, memory),and the software processes and/or services of the terminal device may beconfigured to operate in collaboration with a centralized system device500 (ground station 430/server 450, described above), and maycommunicate with the centralized device either via broadbandcommunication such as wireless or wired (e.g., USB), or via a very lowbandwidth satellite link, particularly as described herein.

Illustratively, the techniques described herein may be performed byhardware, software, and/or firmware, such as in accordance with thevarious processes of device 500 (ground station 430/server 450) and/ordevice 600 (terminal 410), which may contain computer executableinstructions executed by processors 520/620 to perform functionsrelating to the techniques described herein. It will be apparent tothose skilled in the art that other processor and memory types,including various computer-readable media, may be used to store andexecute program instructions pertaining to the techniques describedherein. Also, while the description illustrates various processes, it isexpressly contemplated that various processes may be embodied as modulesconfigured to operate in accordance with the techniques herein (e.g.,according to the functionality of a similar process). Further, while theprocesses have been shown separately, or on specific devices, thoseskilled in the art will appreciate that processes may be routines ormodules within other processes, and that various processes may comprisefunctionality split amongst a plurality of different devices (e.g.,client/server relationships).

FIG. 7 illustrates an example antenna configuration (table) 700 for anantenna 660 according to one or more embodiments herein. For example,the illustrative antenna may be approximately 6 cm×4 cm in size, 5 cm×5cm, or any other suitable size or shape, e.g., with approximately 9 dBiof gain. According to the illustrative embodiments herein, the antennamay operate in the 5.9-6.4 GHz transmission range. The antenna'sillustrative input power is 1 Watt (0 dBW). Also, the peak equivalent(or effective) isotropically radiated power (EIRP) using a 9 dBi antennais 9 dBW (e.g., 7.9 watts). Notably, any suitable antenna configurationmay be used (e.g., 50% duty cycle, etc.), and the parameters shown aremerely an illustrative example for purposes of discussion herein. Notealso, that table 700 is a vast simplification of all of the possibleparameters and configurations of an antenna, and is meant to be merelyfor discussion of an illustrative embodiment herein.

FIGS. 8A-8B illustrate an example earth station terminal antenna gainpattern. The antenna 660 of the terminal 410 (device 600) may beillustratively embodied as a simple, rectangular quad-patch antenna(e.g., 6 cm×4 cm in size) with approximately 9 dBi of gain, as shown inthe configuration of FIG. 7. It can be operated in either the verticalor horizontal polarization, or in both. In the azimuth plane 810 (FIG.8A) or in the elevation plane 820 (FIG. 8B), the pattern 830 isvirtually the same. Moreover, table 900 in FIG. 9 shows an illustrativegain pattern 920 and EIRP 930 for the illustrative antenna of earthstation terminal 600 (e.g., a quad-patch antenna in the XY and XZplane), ranging from 0 to 90 degrees off bore-sight 910.

For further understanding, FIG. 10A illustrates an example demonstration1000 of link margin 1010 in wireless communications. In particular, thebasic concept is that a transmitting radio 1020 transmits a signal withan original transmit power 1025, which on the way through cable 1030 toantenna 1040, experiences certain link loss until the EIRP gain at theantenna. Over the distance of the radio wave, path loss 1050 isnaturally experienced through the transmission medium until reaching thereceiving antenna 1060 (e.g., at an intended receiver or else at anunintended, and thus interfered with, receiver), which amplifies thereceived signal and conveys it through local cabling 1070 to theultimate receiver radio 1080 with a resultant receive power 1085. (Notethat the illustrated path loss shows a linearly decreasing loss rate,but in reality, the curve may be much more complex (e.g., decreasing ata greater rate as the transmission travels further from thetransmitter). For instance, for a simple dot antenna, the attenuation isfunction of R^3, while for a better antenna it can improve to be afunction of R^2.) The difference between the received power 1085 and thereceiver's sensitivity is referred to as the link margin 1010. Saiddifferently, link margin 1010, measured in dB, is the difference betweenthe actual received power and the receiver's sensitivity (i.e., thereceived power at which the receiver will stop working).

Note that in a typical real-world environment, radio communication andelectronics often are subjected to incidental noise (i.e., any signalother than the one being monitored), such as thermal noise, blackbody,cosmic noise, atmospheric noise, etc., as well as and any other unwantedman-made signals. A “noise floor” is the measure of the signal createdfrom the sum of all the noise sources and unwanted signals within ameasurement system. As shown in FIG. 10B, for example, a noise floor1090 is shown based on this incidental noise 1095, indicating the levelof received power (over the receiver's sensitivity) at which thereceiver may begin adequately separate an intended signal from the noise(without advanced separation techniques). The receiver, therefore, maybe configured to simply ignore signals below this noise floor (e.g.,squelching the static/noise). Accordingly, the link margin 1010, asopposed to merely being based on the receiver's sensitivity as in FIG.10A, may be more accurately be based on the receiver's noise floor(i.e., the difference between the receiver's noise floor 1090 and thereceived power 1085). Either calculation for link margin may be usedherein, e.g., depending upon the implementation and configuration of thereceivers, and the techniques herein are not limited to either one.

As described herein, the link margin 1010 (above the receiversensitivity or, preferably, above the noise floor) may be consideredwhen determining link power budget (or simply “link budget”)computations. In general, the link budget equation may be based on asimplified equation where the received (Rx) power is equal to thetransmitted (Tx) power plus gains minus losses:Rx Power (dB)=Tx Power (dB)+Gains (dB)−Losses (dB)   Eq. 1.In the event that the link budget equation results in a receive powerthat is greater than the sensitivity or, more particularly, a noisefloor of an intended receiver, i.e., has a positive link margin 1010,then that transmission should be received successfully. At the sametime, however, should the receive power at an unintended receiver begreater than that unintended receiver's sensitivity or, moreparticularly, a noise floor, then the transmitted signal could interferewith the unintended receiver's operations.

Another simplified, but more complex link budget equation may beestablished depending upon the particular communication environment,such as, for example:20 log D−GT _(az) −GL _(el)—(GR+38)−Pol>T   Eq. 2,where D is the distance between the transmitter and receiver, GT_(az) isthe transmit gain in the azimuth direction to the receiver, GT_(el) isthe transmit gain in the elevation direction to the receiver, GR is thereceiver gain, Pol is the polarization gain, and T is a predeterminedthreshold value, e.g., the noise floor of the particular receiver. Ingeneral, to provide extra protection for unintended receivers, T may beset at some value (e.g., 6 dB) less than the prevailing Boltzmann noise(“noise floor”). Said differently, different values/levels of T may beused for different types of receivers, and also depending on whether thereceiver is an intended receiver or unintended receiver: that is, whencalculating the threshold T for an intended receiver to sufficientlyreceive a transmission, the receiver's noise value (or sensitivity) maybe used, while for an unintended receiver, a precautionary adjustment tothe threshold T may be made, such as e.g., the noise floor minus 6 dB(or some other determined adjustment value). Note that as describedbelow, according to the techniques herein, if the power budget exceeds athreshold T to an intended receiver, but is simultaneously below acorresponding threshold T for an unintended receiver at a givenlocation, then that location/transmission is considered to be acceptable(i.e., reaches the intended receiver, and does not interfere with anunintended receiver).

Additionally of note, the earth is a strong attenuator at microwavefrequencies. Therefore, signals within the C-band that travel towards aPtP receiver antenna will stop either at the point where the signal hitsa hill or at the curvature of the earth. FIG. 11 illustrates an example1100 of line-of-sight communication, where an example microwavecommunication tower 1110 (PtP transmitter 310), illustratively locatedat height “H” above sea-level, produces a line-of-sight 1120 based onthe curvature “X” of the earth. Note further that refraction due toatmospheric pressure along the surface of the earth extends theeffective radio horizon. As such, the techniques herein may also use thestandard” 4/3 earth model” to account for horizon extension due torefraction, as may be appreciated by those skilled in the art.

Specifically, the limiting distance for line-of-sight communicationssuch as microwave communications can be derived by the simplifiedformula:Radio Horizon(mi)=SQRT of (2×Height)   Eq. 3,where the Height (ft.) is the sum of the antenna tower plus height abovesea level. By way of example, the height of a PtP transmit tower mightbe on the order of 50 feet on top of a 300 foot (or so) hill. This woulddefine a maximum communications range (line of sight 1120) of about 26.5mi to a sea level receiver. Various other factors may extend or reducethis number, such as obstructions or receivers above sea-level (thecalculation above assumes a sea-level receiver). For instance, one wouldadd 2.8 miles to this number if a receiver (or conversely, a terminaltransmitter herein) is expected to be held at about 4 feet above theearth. Note that information about terrain (used below) may be obtainedfrom a number of sources. e.g., but not limited to, U.S. GeologicalSurvey (USGS) national maps/topographical information, Google Earth™,and so on. It is also noted that, should the prospective transmitter orincumbent receivers be in a maritime location (e.g., ocean), aeriallocation (e.g., balloon-based networking), or location other than onland, other factors may be taken into consideration with regard to theline of sight, as may be appreciated by those skilled in the art. (Also,in the specific embodiment where the system is used to avoidinterference with a satellite located in a similar angle in the sky, theradio horizon may be set to infinity and need not be factored into thecalculations.)——Avoiding Interference in Wireless Communications——

As mentioned above, the techniques herein provide a robust interferenceprotection regime to ensure that prospective transmitters of one system(e.g., a satellite communication network 400) will not cause harmfulinterference to an incumbent system (e.g., PtP operations in system300). As described below, the techniques herein may determine whether aprospective transmitter 410 will interfere significantly enough withunintended receiving terminals (receivers 310) to cause impermissible orotherwise unacceptable degradation in performance of the incumbentwireless communication system. Said differently, the techniques hereindetermine acceptability of transmission by a transmitter 410 within thepresence of incumbent communication receivers 310 based on the risk ofinterfering with such receivers, and allow or deny such transmission,accordingly. (As mentioned above, and as will be appreciated by thoseskilled in the art, interference with an unintended receiver may bebased on interfering with ground-based PtPRs, a neighboring satellite, aground station associated with another satellite, or any otherunintended receiver where a transmission may raise the noise floor ofthat unintended receiver.)

In particular, as described in greater detail below, based on a databaseof incumbent receiver properties (e.g., the FCC ULS database identifyingPtP operations in the C-band), the techniques herein determine thelocation, altitude above sea level, antenna polarity, and orientation ofeach incumbent receiver 310, and identify a “Protection Zone” for eachreceiver, such that a given patch of earth (or sea, air, space, etc.) isidentifiable as either a) requiring protection against transmission by aterminal 410 orb) not requiring protection against transmission byterminal 410. Once the receiver protection zones are combined withreal-time location information from a terminal 410 seeking to transmit,the system herein may then act accordingly to prevent any harmfulinterference to incumbent (e.g., PtP) operations, while determining oneor more acceptable frequency bands (if any) on which the terminal maytransmit in a given power. Notably, as described below, the techniquesmay be performed based on either a centralized manner (achieved bycollaboration between the ground station 430/server 450 and the terminal410), or localized (decentralized) manner (contained entirely on theterminal 410, given sufficient processing resources), or else within anetwork planning tool (e.g., for placement of a transmitting station ofa new wireless communication system in the presence of an incumbentwireless communication system, where the incumbent wirelesscommunication may require interference protection).

As an up-front illustration of the capabilities of the techniquesherein, FIGS. 12A-12B show an example simplified procedure 1200 foravoiding interference in wireless communications according to aparticular example embodiment herein. (Note that the procedure 1200 ismeant as an example demonstration of a particular embodiment of thetechniques herein in order to frame an understanding for the moredetailed description below. The steps shown in FIG. 12A-12B are notmeant to be limiting to the present disclosure, and additional, fewer,simplified, more complicated, and/or entirely different steps may beperformed by the systems herein in accordance with various aspects ofthe techniques herein.)

In particular, example procedure 1200 begins in step 1205 of FIG. 12A atthe ground station, and then proceeds to step 1210 populate the groundstation 430 (or server 450) with all of the necessary information aboutthe incumbent receiver network 300 in order to determine (e.g., draw)protection zones (for each channel/polarity and intended receiver) instep 1215 defining all of the locations where a terminal 410 mightinterfere with each known incumbent receiver 310 (e.g., based on linkbudget, as described below). In step 1220, the ground station mayenlarge the computed protection zones for added protection, and then instep 1225 may reduce the coverage of the zones based on geographicalcharacteristics, such as line-of-sight considerations for curvature ofthe earth and terrain mapping (e.g., hills, mountains, etc.). Since theprotection zones at this point may be a series of complicated curves andcontour lines, and since the terminals 410 may have limited resources(e.g., memory), in step 1230 the ground station may simplify therepresentation of the protection zones into a less preciserepresentation (format) that is consequently less data-intensive, suchas a more simplified polygon representation or angular/distancerepresentation based on major and minor horizons (described below). Thefinal representation of the protection zones may then be sent to (orotherwise retrieved by) the terminals 410 (e.g., initial configuration,download over higher-bandwidth links, etc.) in step 1235.

Now, in FIG. 12B, procedure 1200 continues at the terminal 410 where thefinal representation of the protection zones is uploaded or otherwisereceived and stored by the terminals (step 1235), such that whenever theterminal 410 wishes to transmit on a potentially interfering frequencyband, it first determines its location in step 1240, then checks whetherthat location is within any protection zone of any incumbent receiver instep 1245. If so, then in step 1250 the terminal may locally calculatewhether it might actually interfere with the receivers corresponding tothe protection zones, since, as mentioned above, much of the precisionof the protection zones (based on link budget, terrain, etc.) may havebeen lost through the simplification of their representation. As such,based on the local determination (step 1255) that interference would notbe an issue, or else based on not being in a protection zone at all instep 1245, the terminal 410 may transmit on a cleared frequency band instep 1260. Otherwise, transmission is not allowed, and the illustrativeprocedure 1200 ends in step 1265. Note that other measures may beconsidered to allow transmission, including adjusting the terminal'slocation, transmit properties (e.g., diverse polarity, reducedtransmission power, etc.), and so on, but such optional enhancements aredescribed in greater detail below. Note further that as mentioned above,the steps of procedure 1200 are merely an example of a particularembodiment, and are not meant to be limiting to the scope of the presentdisclosure, as many alternatives to the above configuration of steps maybe conceived as described below.

As mentioned above, the techniques herein start with acquiringinformation about the incumbent system 300 for which interferenceprotection is desired. This information, notably, may be computed by,and stored in, either the ground station 430 or in server 450, and anycombination of their cooperation is conceived herein (e.g., computationon server 450, and storage on ground station 430, etc.). In particular,in an illustrative embodiment, the construction of this information maybe performed by an offline tool associated with the system, meaning itcan be done in the server 450 or calculated offline and then loaded intothe server/ground station 430. Similarly and without limitation, thecomputations can be performed in the cloud, such as on the Amazon WebServices (AWS) or similar cloud based servers and storage, as may beappreciated by those skilled in the art.

According to an illustrative embodiment, a database 460 may contain allof the required information for all the receivers of the incumbentsystem 300 (e.g., PtPRs in the US) which allow the system to calculatethe protected zones, as described below. For instance, in theillustrative embodiment of PtPRs, this information may be stored in theFCC's ULS database as mentioned above, which contains an up-to-dateaccount of Fixed Service PtP licensed pairs and applicant pairs (e.g.,in the C-band, or other overlapping frequency band with system 400) andtheir associated identification (e.g., call signs). This information,notably, includes the coordinate locations/orientation of PtPRs, thefrequencies of the PtP communication (e.g., frequency center and width),and antenna height, height above mean sea level (base altitude),receiver polarization, antenna type, and optionally other information,such as azimuth, gain characteristics (lobe shape), and so on for eachPtPR antenna. (Note that if such information is not directly within thedatabase 460, the system herein may compute such values based on publicknowledge of antenna characteristics, or else based on variousassumptions thereof. Also, for embodiments where the system ensures thatthe transmitter does not interfere with the operations of another nearbysatellite, the locations of geostationary satellite are well known whilethe momentary locations of non-stationary satellites can be calculated.)

Periodically (e.g., daily), the system (e.g., server 450) accesses thedatabase 460 (e.g., the FCC ULS database) and obtains the most recentlyupdated licensing and applications information in the frequency band ofinterest (e.g., C-band in our case). This information is used by thesystem to construct a relevant server-side database 543, which containsupdated information regarding all active (and pending) receivers (e.g.,PtPRs) and their location, altitude of antenna base, antenna heightabove ground, azimuth, antenna type/gain, diversity height polarity, andfrequencies assigned to the incumbent receiver. Notably,channels/frequencies used by a specific PtPR may change, such as when asegment of a network requires additional bandwidth and as such acquiresan additional frequency channel. Also, it should be noted that at timesthere can be changes to the location, azimuth, height, antennainformation, etc. in the ULS database (e.g., correcting errors, updatingwith greater accuracy, accounting for actual changes or plannedmovements, changes in polarity, and so on).

Additionally, the system also maintains a current map of the coveredarea (also within illustrative database 543), which may illustrativelyinclude geographically significant features, such as terrain (e.g.,hills, mountains, valleys, and other topographical information that maybe relevant to line-of-sight calculations described below). As notedabove, such information may be obtained from various sources, and mayalso be updated as deemed necessary.

As described in greater detail below, the server database 543 containsthe information that may be used to create a detailed representation ofprotection zones, that is, locations where a terminal 410 couldpotentially interfere with an incumbent receiver 310 (e.g., on aparticular frequency band/channel). These protection zones for eachreceiver 310 may notably be computed (and subsequently referenced) perintended receiver (e.g., per satellite), per incumbent receiver polarity(e.g., horizontal and/or vertical), and any number of other factors thatwould vary the potential for interference (such as, e.g., differentlevels of uncertainty or “smearing”, described below). For instance, theset of unintended receivers for which a transmission on “channel 1”would interfere would be different from those that would be potentiallyinterfered with by a transmission on “channel 2”. Additionally, acomputation of interference at one unintended receiver at a horizontalpolarity would be different from that at the same unintended receiver ata vertical polarity. Furthermore, a computation of interference for atransmission to an intended receiver (satellite) in one location (e.g.,azimuth) would be different (for the same unintended receiver) than atransmission to another intended receiver in a different location. Thetechniques described below, therefore, may be applied for each of thesedifferent inputs and in different combinations, both in terms of initialcomputation and for subsequent reference (as would be necessary, thatis, based on available transmission possibilities by the terminals 410,such as, e.g., whether the same channel is available on differentreceivers/satellites, or whether the terminal can transmit on differentpolarities, etc.). As such, while certain considerations for suchfactors may be explicitly described below, it is important to note thatthe generalized portions of the description below assume that thepotential for interference may be based on such factors, and the serverdatabase 543 (and corresponding local database 643) may provide theadequate distinctions in transmission configurations with regard totheir corresponding potentials for interference (protection zones),accordingly.

It is important to note that servers 450 can compute, in advance,exactly on a map where a terminal 410 is allowed to transmit (and notinterfere with any receiver 310) based on link budget calculations usingantenna properties, transmitter properties, communicationcharacteristics, and so on. However, since at the time of computing thisinformation the servers would not know where a mobile terminal would be,and since the terminals themselves would generally not have enoughstorage to keep a complete record of this information, the techniquesherein may calculate approximated protection zones representing apotential for interference, where the terminal 410 (e.g., a mobiledevice) may then be responsible for determining for itself whether it isallowed to transmit. For example, the terminal 410 may calculate thelink budget to each receiver having an approximated protection zone thatcovers the terminal's current location (described further below). (Notealso that in one embodiment, the terminals 410 may have sufficientresources for precise mappings of all acceptable transmission locations,at least within a given region, as also described below.)

According to the present disclosure, two illustrative techniques forcomputing the approximated protection zones (i.e., a potential forinterference) are described, namely, a simplified geometrical approachbased on antenna properties, and, as a preferred embodiment herein, amore sophisticated link-budget-based approach. (Notably, otherapproaches may be used, including, but not limited to, various hybridcombinations of the details aspects from each approach describedherein.)

Regarding the simplified approach first, FIG. 13 illustrates an examplereceiver acceptance cone (RAC) 1300. (Note that one interferes withreceivers, not transmitters, so the receiver side of the link is theonly acceptance cone at issue.) The RAC, based on receiver antennaproperties and configuration, is the coverage area corresponding to aregion, in a particular direction of coverage (noting that certainreceivers may be configured with more than one direction of coverage,and thus resulting in multiple coverage areas), for which a receiver isconfigured to receive (accept) a transmission. Though the intent is thatthe opposing transmitter (e.g., PtPT 305) may generally be placed within(e.g., and pointing along) the RAC 1300 of its corresponding receiver(e.g., PtPR 310), the RAC 1300 also implies a region in which athird-party transmitter (with a specific transmission power) mightinterfere with the receiver 310. Said differently, the RAC 1300 alsodefines an area, where outside of this area the receiver 310 may not beadversely affected by a terminal 410 operating at the same frequencyband as the receiver (e.g., and at a predetermined transmission power).(Note that RAC 1300 represents a simplified region and is forillustrative purposes only, particularly since antennas have side-lobeswhich need to be factored into protection zones, as described below.)

As shown, the maximum communications range for a transmission is thedistance “D” (e.g., 30 miles), defined for microwave frequencies by thetransmitter antenna's height above sea level, the topology of the area,and the curvature of the earth, as mentioned above. The angle of theRAC's inclusion triangle is defined by the receiver antennacharacteristics. For example, PtP microwave antennas are typically twoor three meters in diameter, which defines a 1.7-degree (or less)acceptance angle (3 dB), so illustratively an angle of 2 degrees (+/−1degree) is shown. Note that the receiver database (e.g., FCC ULS)contains information regarding smaller or larger receiver dishes andother parameters (e.g., antenna apertures), and this data may be usedwhen accounting for the RAC of any given receiver. As shown, RAC 1300for this specific example covers approximately 16 square miles, and isapproximately 30 miles long away from the receiver with an approximately1-mile wide maximum spread.

The RAC 1300 is an intended focal range for a receiver 310, within whichthe receiver is designed to receive transmission signals, andaccordingly attenuate interference signals from transmitters outside theRAC. However, in order to provide additional assurance and protectionfrom interference, the techniques herein may be configured to assume anexpanded protection region beyond the RAC 1300 of FIG. 13. For instance,in this first simplified embodiment, as shown in FIG. 14, a receiver's“protection zone” 1400 need not be limited to the RAC 1300, but may beexpanded to a larger region to provide extra protection againstinadvertent interference. In particular, an expanded protection zone maybe constructed to account for inaccuracies in various measurements suchas measurement of the direction in which the transmitter points, GPSlocation, height of the transmitter, etc. For example, in one embodimentas shown, the expanded protection zone 1400 may span an acceptance angleof approximately 20-degree arc (+/−10 degrees, rather than merely +/−1degree, i.e., ten times larger and 1/18 of a 360-degree circle), and mayextend for an additional distance (e.g., 50 miles or more, particularlydepending upon antenna height, rather than merely 20-30 miles),resulting in a coverage area of approximately 450 sq. miles (notablylarger than the RAC's 16 sq. miles), a substantial safety factor inaddition to the physical RAC.

Note also that antennas (even those that are highly directional innature) may have side lobes (also back lobes) that extend in otherdirections as mentioned above, even in a direction opposite the intendedcoverage area or RAC 1300. To account for such side lobes to ensure thatthe terminals 410 will never cause harmful interference—even at veryclose proximity, the extended protected area 1400 may also includeadditional coverage areas 1410 in one or more other directions. Forinstance, in one simplified embodiment as shown, the additional coveragearea 1410 may account for such side lobes by adding a fixed-radiuscircle (or one or more other polygonal regions) about the receiver 310,to account for such side lobes. This may be considered part of theexpanded protection zone 1400, and any prospective transmitter withinsuch areas may also need to be accounted for interference purposes, asdescribed below. Based on example PtPR side lobe properties, theadditional coverage area 1410, which may be considered a “closeproximity circle” surrounding the PtPRs, may have an illustrative radiusof approximately 3.9 miles. (Note, any suitable radius for thisadditional coverage area may be used, such as depending on the receiverantennas, transmitter power, etc., and this illustrative andnon-limiting example of 3.9 miles was selected based on an example of aminimum side-lobe stand-off distance calculated according to anillustrative configuration, described below.)

Furthermore, according to one or more aspects of the disclosure,additional margins of error may be provided in the expansion of a RAC1300 into a protection zone 1400 to allow for extra protection of anincumbent network. For example, in terrain mapping, it may be assumedthat the transmitter and/or receiver is located at a height higher thanwhere it would actually be located (e.g., for a handheld device, theelevation of the transmitter above the earth at the given proposedlocation may be a few meters (taller than a person), and/or the heightof the receiver may also be assumed to be higher than it actually is).Also, other factors of estimation or error, such as transmitter angle,transmitter location, receiver placement, receiver's physicalproperties, and so on, may benefit from a forgiving margin of error ontop of the RAC 1300 or even on top of an already expanded protectionzone 1400. As such, the protection zone 1400 may be additionally basedon various margins of error (e.g., percentages, set values/multipliers,administrator-defined ranges, measured errors, and so on).

The first illustrative (simplified) protection zone 1400 described abovemay thus range from the RAC 1300 up to a pre-defined expanded range,including any additional areas 1410 based on antenna properties (e.g.,antenna lobe patterns including main lobe and side lobes), and may beused to determine whether a transmitter 410 is within an area in whichit may interfere with a receiver 310. (Note that in some cases, theprotection zones may be effectively limited to areas on the earth'ssurface, though in other cases, the protection zone may be considered toextend in elevation, as well as azimuth, and this may be similarlyaccounted for.)

Notably, a more accurate (and generally more preferred) determination ofa zone of potential interference is to calculate the RAC as theinteraction between the pattern of the antenna of the transmittingterminal and the antenna of the specific PtPR, assuming the given(nominal) transmission power of the terminal. Regarding this moresophisticated (and preferred) link-budget-based approach for calculatingprotection zones, recall that the servers can compute, in advance,exactly on a map from where a terminal 410 is allowed to transmit(without interfering with any receiver 310). While this is certainly oneconceived manner of attacking the problem in one embodiment herein, inanother (e.g., preferred) embodiment, the techniques herein need only todetermine the locations wherein the calculated link budget equals (orsurpasses) the noise floor for each receiver, and define this line asthe boundary of the protection zone. In particular, in this illustrativeembodiment, the boundary of a receiver's protection zone may be based onapplying a link budget equation for transmission from the 410transmitter to the intended receiver (e.g., satellite) 420, in order todetermine the distance from the receiver 310 at which point a noisefloor is exceeded at the receiver 310 (i.e., interfering with theoperations of receiver 310).

For instance, for each known receiver (e.g., PtPR) 310, the systemcalculates the farthest horizon distances at which a terminal 410 couldinterfere with the receiver. To do this, the system calculates a“protection zone” polygon around the position of the PtPR. This is doneby calculating, at small angular increments (e.g., 1-degree increments)for 360 degrees around the receiver location, the distance at which theresult of the link budget calculation along that radial is exactly equalto the noise floor. Any closer to the PtPR along that radial, thetransmitter could possibly interfere with the operation of the PtPR, andconversely transmitting from farther away along the same radial wouldnot interfere with that PtPR.

The specific shapes of the polygons are governed by the link budgetinteraction between the lobes of the incumbent receiver's antenna andthe lobes of the terminal's antenna, and assuming that the terminal ispointing towards a specific intended receiver (e.g., satellite). Forexample, FIG. 15 illustrates a simplified example of antenna lobes froman antenna site 1500, where a main lobe 1510 may be the intendedtransmission and/or reception focus, but various side lobes 1520 andback lobes 1530 may also result from the antenna design (and radiocommunication principles). Additionally, FIG. 16 illustrates an examplegain pattern 1600 for an example (e.g., 2-meter) PtP microwave dish.(Note that this radiation pattern is typical for a microwave antenna,with side-lobe signals being generated at significant levels at azimuthangles out to +/−90 degrees.) As such, the techniques herein compute thenoise floor “interference boundary” (protection zone) based on theantenna lobe pattern of the associated antennas of systems 300 and 400,and based on the particular directions of the antennas, and the expectedtransmission direction and power of the transmitter.

The techniques herein may first determine a typical received signalnoise power of an incumbent receiver 310 (e.g., PtPR), and then candetermine the link budgets necessary to maintain a transmitted signallevel from a terminal 410 sufficiently below that noise floor. Forinstance, a high performance receiver 310 will have a best case Boltzmannoise floor equal to approximately −174 dBm/Hz. Now, by adding in 6 dBof noise immunity (or some other chosen level of noise immunity), and anexample signal bandwidth of 8 MHz (e.g., 69 dB), then the techniquesherein define a new and more robust noise floor threshold which is 6 dBmore noise than Boltzman noise, or:Noise Power=−174+69+6=−99 dBm   Eq. 4.With this (or any other suitably) computed power value, and using anysuitable link budget equation based on antenna lobe patterns, thetechniques herein can now compute the location along each radial from areceiver 310 at which a transmission from the terminal 410, aiming at anintended receiver (e.g., satellite) 420, would cross (i.e., is equal to)the noise floor, interfering with the incumbent and unintended incumbentreceiver. (That is, determining the location where the terminal's poweris the same noise power as the Boltzman (natural) noise level at thereceiver). Illustratively, recall that the actual “crossing” of thenoise floor may illustratively be based on a safety margin (e.g., 6 dB),for added assurance of non-interference. Said differently, the potentialfor crossing the noise floor may be based on an artificial “safe” noisefloor value, and not the actual noise floor of the receiver.

As an aside, the power value may also be used to calculate an absolute“stand-off distance” (D) from a receiver, particularly for locationsnear (behind and to the side of) the receiver as described above, suchas should a transmitter be aimed directly at the receiver. For example,based on various known antenna lobe link budget equations, and using the6 dB safety margin, this value may result in a behind-the-dish stand-offdistance (D) of 630 meters, and for the side-lobes a stand-off distance(D) of 6300 meters (3.9 miles). This means that the transmission of aterminal's signal from any distance greater than 630 meters behind thedish and/or 6300 meters to the side will result in a received signal of6 dB or more below the Boltzmann (natural) noise floor at the incumbentreceiver. (Note that this maximum stand-off distance (e.g., 3.9 miles)could be used to establish the additional safety range 1410, asmentioned above with reference to the “simplified” protection zone1400.)

Returning to the discussion of the link-budget-based protection zone,once the link budget computations are completed for a receiver (in all360 degrees around the receiver), each distance and angle may then beconverted to latitude and longitude, which results in a polygon thatrepresents the transition boundary of the protection zone for thatparticular receiver (e.g., for a particular transmitter azimuth to agiven intended receiver, at a particular polarity, etc.). This boundarycan then be overlaid onto a map, where points inside the polygon areinside the protection zone, and points outside are not inside theprotection zone. Said differently, as a result of the computationsabove, the server 450 may obtain numerous polygons which describe thepotential interaction between each receiver 310 and terminal 410attempting to transmit towards a given receiver (e.g., satellite) 420 ata specific frequency channel and nominal power. Note that theseprotection zone polygons may be stored in a database of the groundstation 430 or in a server 450, however may generally not be transmittedto the terminals in this form; rather they may first be modified (e.g.,simplified) as described below, since the detailed description of thesepolygons may consume too much memory and may require high networkbandwidth to update. (Note further that in one embodiment, theseprotection zone polygons are not stored in the gateway/server, either,and need only be calculated for further processing and storage in adifferent format, such as described below.)

FIG. 17 illustrates an example polygon 1700 resulting from link budgetcalculation towards a single receiver 310 (e.g., overlaid on a map), fora given frequency band, polarity, and intended receiver azimuth (e.g., aparticular satellite 420). That is, the resultant polygon 1700represents a noise floor crossing boundary of a particular receiver 310for a given transmission configuration from a transmitter (terminal 410)in surrounding geographical locations. As can be seen, a main lobe ofinterference extends generally northeasterly, in an example direction ofthe antenna of the receiver 310 for intended reception.

Note also that the polygon in the proximity to the receiver is a complexpattern (and, notably, need not be limited to areas bounded only bystraight lines). This is due to the interaction of the transmitter'santenna lobes from the various locations along that complex curve,pointing at an illustrative receiver (e.g., satellite) 420, which may bein a southerly direction (e.g., a geo-synchronous satellite). At thesame time, based on this southerly pointing of the transmitter, it canbe seen that the southern-facing side lobes of the receiver 310 are muchless prevalent as a potential for interference (i.e., the transmitterwould be aiming away from the receiver from those locations).

As noted, the pointing angle (azimuth, elevation) of the terminal 410(terminal antenna 660) relative to the incumbent receiver 310 changesthe link budget calculation. Accordingly, each intended receiver (e.g.,satellite) 420 to which the terminal may be pointed changes the resultsof the link budget calculation for a terminal location. Therefore, eachincumbent receiver will have somewhat different protection zones foreach intended receiver (e.g., satellite).

Specifically, with regard to intended receiver (e.g., satellite)diversity, the illustrative satellite-based system herein may operateinitially with two or three geostationary satellites. For instance, toprovide diversity and to manage occlusions from mountains or otherobstructions, the illustrative system may employ one geostationarysatellite in the westerly direction, and one in the easterly direction.An example of such intended receiver orientation from a terminal isshown in FIG. 18, where a terminal 410 at any particular location maypoint at (aim at) each of the intended receivers at a slightly differentazimuth and elevation appropriate for the corresponding satellite, e.g.,a southwesterly azimuth 1810 to satellite 420-1, and a southeasterlyazimuth 1820 to satellite 420-2. (As described below, the terminal (orserver) may select the best available satellite based on location andother factors.) Using the illustrative locations of examplegeostationary satellites, the difference between azimuth 1810 andazimuth 1820 may result in a 40-degree to 60-degree difference inazimuth look angle. As such, the resultant protection zones 1700 basedon link budget calculations as described above could vary significantly,and as such may require separate computations depending upon whichintended receiver is being considered.

It is important to note again that the link-budget-calculated protectionzone boundary is governed by one or more (or illustratively all) of thefollowing:

-   -   On the receiver:        -   location (latitude/longitude);        -   antenna azimuth;        -   antenna polarity; and        -   antenna gain definition for all angles around the receiver;        -   (—and, in certain optional embodiments, the antenna            elevation and the antenna gain defined for all angles around            the receiver).    -   On the terminal:        -   location (latitude/longitude);        -   antenna pointing direction (azimuth and elevation);        -   transmit antenna gain definition for all angles 0-360 of            azimuth and elevation;        -   power output of the transmitter; and        -   transmitter antenna polarity.

Note that channels/frequencies do not affect the calculation of theactual protection zone (that is, if a frequency is changed/added in theULS database, it does not affect the protection zone calculation or thehorizon calculation). However, since the protection zones are referencedby frequency/channel (e.g., transmitting on “channel 1” would notgenerally interfere with a receiver configured to receive “channel 2”),it is also important to keep accurate record of the receiver frequencyband/channel.

Those skilled in the art would also recognize that similar protectionzones can be computed to ensure that the transmission does not interferewith receivers of other satellites which may be in the sky in an angle(elevation and azimuth) proximity to the intended satellite, as notedabove.

According to one or more embodiments herein, the techniques herein mayalso compensate for any potential inaccuracy in the sensors of theterminal 410, such as, for example, the GPS location, the direction atwhich the mobile device points (azimuth), and the elevation relative tothe horizon (tilt angle towards the satellite), and so on. Inparticular, to prevent any of these inaccuracies from misleading theterminal into thinking that it is not in a protection zone (whereterminal transmission would not adversely impact any PtPR), thetechniques herein may perform a “smearing” operation which expands thesize of the protected zone (as denoted by the polygons 1700 above).

In one specific embodiment, the techniques herein include a smearingoperation on the table of the terminal's transmitter antenna gainrelative to the direction of incumbent receiver 310 (e.g., PtPR), andthe tilt (elevation) of the transmitter toward the intended receiver 420(e.g., satellite) relative to the horizon. However, in general thisoperation may factor in the uncertainty of the terminal's GPS location,the uncertainty of the azimuth of the intended receiver/satelliterelative to the terminal's current position (which may come from thecompass reading of the terminal, or from any other suitable azimuthsensor and/or calculation, and the uncertainty in elevation relative tothe horizon (tilt angle towards the satellite).

This smearing process is meant to ensure that even in the worst case ofany of these errors (or the combination of these errors), the systemwould still prevent a terminal 410 from interfering with any of thereceivers 310. To this end, the protection zones (polygons) 1700calculated through the link-budget-based approach above may be expandedby varying the above parameters and expanding the protection zone forthe worst case that could be caused by errors in the terminal's sensorysystem. Note that in accordance with yet another embodiment, the systemmay also bring into account the shaking of a user's hand by adding afixed angular smear factor (such as, e.g., +/−5 degrees), and using thisinformation to expand the protection zone even further.

FIG. 19 illustrates an example of how smearing may affect the protectionzone 1700, by expanding it in certain directions (e.g., “1700+”) tocompensate for any potential inaccuracy. As shown, for illustrationonly, this particular expansion as shown in FIG. 19 results in a generalextension of the protection zone along each of the radial directions ofthe original zone 1700. However, actual computations of the zone basedon smearing factors being input into the calculations above may resultin a slightly different shape of the polygon, a different proportion ofexpansion, and perhaps with different expansion affects in differentdirections (e.g., greater along the main lobe than along the side lobes,etc.). For example, illustrative computations may be made (for eachsatellite) for a 0 az (zero azimuth) and 0 el (zero elevation) (nosmear, e.g., FIG. 17), as well as for a +/−30 az and +/−5 el antennasmear, and a +/−180 az and +/−5 el antenna smear. Such differentazimuth/elevation smearing for the same unintended receiver/PtPR wouldthus result in different protection zones 1700/1700+. Accordingly, theexpanded zone 1700+ is merely a visual example of how protection zone1700 may be expanded, and is not meant to be limiting to the embodimentsherein.

It should be noted that in one or more embodiments herein, the relativeheight of the terminal 410 with respect to the incumbent receiver 310need not be factored into the smearing equation above, in order toreduce the computational complexity of the system. Rather, certainembodiments of the techniques herein may assume that that the terminaland the incumbent receiver are at the same altitude. This assumption isvalid because when the terminal is at close distance to the receiver,the link budget is very high and the terminal is within a protected zoneanyhow. On the other hand, when the terminal is far away from thereceiver, the relative height of the mobile with respect to the receiveris much smaller than the distance. This results in a negligible lowangle between the line of sight of the terminal to the receiver'santenna and the horizon. At the same time, however, should the height ofthe transmitter create a more substantial difference, such as for UAVsor other flying vehicles, then the relative height may be an importantfactor. Accordingly, whether to account for the relative height of theterminal may be configured on an implementation-by-implementation basis.For instance, in one particular embodiment, the system may use anelevation smear value, such as +/−5 degrees, that takes into account thepotential elevation difference.

Generally, in the specific satellite network example implementation, ifthe terminal is actually above the altitude of the incumbent receiverantenna, the elevation won't be an issue because the terminal would bepointing up to the satellite (and away from the incumbent receiverantenna). However, if the terminal is lower than the incumbent receiverand closer to it, the terminal could be transmitting much closer to theantenna, especially in a mountainous area where the terminal is in avalley at the base of a mountain and the incumbent receiver (e.g., PtPR)is on the top of the mountain. One way to handle this would be aprogressive smear of the elevation table for the incumbent receiver, sothat the closer the terminal is to the incumbent receiver antenna, themore it can be smeared.

Notably, in certain embodiments (e.g., the preferred embodiment), theprotection zone polygon 1700 need not be stored in the server database543 or transmitted to the terminal (for local database 643), and insteadmay be used as a boundary around the incumbent receiver 310 within whichthe elevation of each geographic point may be evaluated to determine ifthat point is visible from the incumbent receiver or not. As describedbelow, therefore, the distance of the farthest point within theprotection zone that is visible from the line-of-sight receiver (e.g., aPtPR) is then stored in the database as a horizon.

Microwave communication, in particular, is line of sight, and iseffectively blocked by earth features that are in the line of sightbetween the terminal 410 and the incumbent receiver (e.g., PtPR) 310.Topology mapping/information about the terrain in which the incumbentnetwork 300 operates is known, and as mentioned above, information aboutthe topology of the terrain is available to the server 450. (Note thatin accordance with a specific embodiment, topographic information mayalso exist in the terminal, such as partial information (e.g., based onsmaller map areas or less detailed information), and used as describedbelow.)

According to one or more embodiments of the disclosure herein, thetechniques herein may factor in the topographical layout associated witheach incumbent receiver 310. That is, in the previous steps above, theprotected zones (polygons 1700) were calculated without bringing intoaccount the topology of the area, and as such, the previous calculationswere made under the assumption that the incumbent receivers 310 andterminal 410 operate on a flat plain (e.g., receivers 310 at theirdesignated altitude above sea level, and the terminal 410 at sea level,but without any terrain features between them). In reality, variouslocations within the protected zones which were calculated in theprevious steps may actually not need to be included in the protectedzone because some topological feature (e.g., a higher hill or the actualhorizon based on the elevation of the surrounding terrain) obscures aline of sight from that location to the incumbent receiver.

FIG. 20 illustrates an example cut-away view 2000 of an illustrativeterrain/topology 2010 along the line 2015 from an incumbent receiver 310to any point within its example protection zone 1700 (e.g., along themain lobe). (Note that any protection zone may be used, such assimplified zone 1400 above or, preferably, the extended protection zone1700+, and the view in FIG. 20 is merely an example for discussion ofthe techniques herein.) Locations 2020 from which there is a line ofsight from the location on the ground towards the incumbent receiver 310are marked with a hashing, and locations 2030 which are hidden from thereceiver 310 have no such hashing.

According to the techniques herein, therefore, terrain around anincumbent receiver 310 may be mapped by sampling the ground elevation inradials every r degrees around the receiver location (starting at theincumbent receiver and extending outward from the incumbent receiver).Terrain mapping is location-dependent rather than link-budget-dependent,so it only has to be done once per location (per incumbent receiver),optionally limited to processing elevations within calculated protectionzones (which differ by smear value, incumbent receiver azimuth, andintended receiver/satellite for a particular location). The elevationmapping only needs to know the status of terrain points (visible or notvisible to the incumbent receiver). Notably, however, keeping a statusfor each individual point in the radial is data intensive.

Instead, therefore, the techniques herein also propose a method of usingthe slope (line 2025) and distance from the incumbent receiver toblocking elevations. For example, if the maximum slope is set to −999(which is practically straight down), elevation may then be sampledevery n meters moving outward from the receiver. For each sample point,the slope from the incumbent receiver to the point is calculated. If thecalculated slope is less or equal to than the current maximum slope,then that point is not visible to the incumbent receiver 310, since theelevation point where the current maximum slope was generated would beblocking that point. If the calculated slope is greater than the currentmaximum slope, then that point is visible to the incumbent receiver, andit is set to the new maximum current slope. Sampling proceeds outwardsfrom that point with the slope calculated at each point, until thecalculated slope is less than the current maximum slope. This representsa blocking elevation, and is stored with the slope value and thedistance from the incumbent receiver. Sampling continues out the radialuntil the maximum possible horizon is reached. For example such amaximum might correspond to the maximum distance that two 4000 m peaks(with sea level elevation between them) would be visible from eachother, which is approximately 450 km. (Note that optimizations can bedone in addition or in the alternative to sampling only within thecalculated protection zones, such as using the actual elevation of theincumbent receiver location, among others.)

The topology-based actions above result in a set of [distance, slope]pairs, where for any point along the radial, the visibility can bedetermined by finding the two [distance, slope] pairs that the pointlies between, calculating the slope from the point's distance andelevation to the incumbent receiver, and comparing it to the slope ofthe [distance, slope] pair closer to the incumbent receiver. If theslope of the test point is greater than the closer [distance, slope]pair, then the point is visible from the incumbent receiver, otherwiseit is not visible.

This provides a technique for calculating the visibility of theincumbent receiver from any point around using slopes. For preciseimplementations (e.g., no forgiveness for interference), error should bemade toward the point being visible rather not visible, becauseinterference with the incumbent receiver (e.g., a PtPR) must be avoidedat all costs. Using this method, missing a [distance, slope] pair causesmore terrain to be revealed rather than obscured.

As the distance from the incumbent receiver increases, so does thedistance between adjacent radials. To avoid missing lower areas betweensampled points, each of the points are sampled perpendicular to eachside the radial at increments of “n” meters up to half the distance tothe next radial, and the lowest elevation value is used. (Note that inone illustrative example, both the highest and lowest elevation valuesmay be used: the highest for testing the visibility, and the lowest fordetermining the slope.)

The last [distance, slope] value for a radial gives the maximum horizonfor the radial. Any of the values in between it and the incumbentreceiver can be used to increase the amount of blocked area; ignoring a[distance, slope] value simply decreases the amount of blocked area thatis calculated.

The maximum [distance, slope] value for the total set of radials can beconsidered to be the maximum horizon for the location of the specificincumbent receiver (e.g., PtPR), since from no direction is theincumbent receiver be visible beyond that distance. This is defined tobe the “Maximum Horizon” for an incumbent receiver. Note that thisapplies primarily for terrestrial PtPRs; when dealing with a PtPRincumbent receiver in the sky, e.g., a satellite, the correspondinghorizon may be based on the height/altitude of the satellite applied tocorresponding three-dimensional horizon calculations, accordingly. Notefurther that a satellite may be also affected by local topology. Forexample, if a satellite is placed on the sky over Hawaii, it may appearfor some users (for example users in Colorado) as being low above thehorizon and as such it may (or may not) be obscured by a mountain.

Notably, terrain mapping calculations also take into account curvatureof the earth when calculating the blocked distances (e.g., using astandard 4/3 earth model to compensate for surface refraction effects).

Referring again to FIG. 20, the cross section associated with a specificazimuth from a specific incumbent receiver towards a terminal's locationon the ground is shown. Despite the fact that the protection zone 1700may mathematically extend up to 125 km, the topology map indicates thatmore than 75 % of the places along the specific azimuth (areas 2030) canbe safely excluded from the protected zone. Different azimuths will havea different cross section, and as such, identify different areas thatcould be excluded from the protected zone 1700.

According to one or more embodiments herein, the server 450 may thuscalculate the topological cross sections for each incumbent receiver 310radially at small increments (e.g., on 1-degree increments) around theincumbent receiver's location up to the intersection of the radial withthe protection zone polygon 1700. Referring to FIG. 21, therefore, whichillustrates the completely blackened areas 2110 on the map to show thelocations that were in the protection zone 1700 (with respect to thegiven incumbent receiver and specific channel and based on the linkbudget calculation) which have a line of sight towards this specificincumbent receiver. The hashed areas within the protection zone 1700 nowindicate locations which could be excluded from the protection zonebecause the topology obscures the incumbent receiver, and as such, thereis no line of sight from these locations towards the incumbent receiver.

Notably, in the illustrative embodiment, the server 450 calculates thepolygon boundary 1700 for all incumbent receivers where the link budgetis equal to the noise floor, prior to calculating the reduced coverageof areas 2110. This keeps the amount of terrain data that is computed toa minimum. However, in alternative embodiments, the server may firstcompute all lines of sight regions from incumbent receivers, and thencalculate the portions of those visible regions that meet thelink-budget equations above. The end result would be the same, and it ismerely a matter of computational preference.

Note further that according to one or more embodiments herein, terrainmapping reductions can be applied selectively in areas, such as wheremultiple protection zones overlap to give better channel selectionoptions. Moreover, since terrain mapping information does not change, itcan be downloaded a single time into the terminals 410 for the regions(or for specific incumbent receivers) where it has the greatest benefit,such as near mountainous areas, and used by the terminal as describedbelow.

In accordance with a preferred embodiment, the link budget calculationand the topological line of sight horizon calculation may be performedin the server 450 or in offline cloud-based servers. Generally, the sizeof the server database 543 that would contain all of the details of thecalculated link-budget protection zones 1700 and/or line-of-sightreductions to coverage area 2110 would often be too large to store inits entirety within local database 643 of a terminal. In addition to thesize of the database, the calculations required to determine the impactof the topology on protected zones may also make it impractical to usethe entire server database data in the terminal. Though in certainembodiments contemplated herein, sufficient resources (e.g., CPU andmemory) may, in fact, be available on the terminals 410, and thecomplete server database may be stored on the terminal for computationof terrain-based line-of-sight computations, more likely embodiments mayconsist of a hybrid approach, where only some of the terrain data isstored on the terminal, as noted above. Furthermore, based on the factthat the information about the incumbent system may change (e.g., thelarge FCC ULS database may change), it may not be practical to updatethe entire database over a low-bandwidth (e.g., satellite) communicationchannel.

In order to reduce the necessary size of the terminal's local database643, and in order to reduce the amount of data transmission to theterminal which may be required in order to update it for changes in theinformation (e.g., the FCC ULS database), the techniques hereinintroduce the concept of major and minor horizons (described below),which are calculated in the server 450 as a compressed representation ofthe relevant the areas 2110 within the protection zone which have a lineof sight to the incumbent receiver, and passed to the terminal in lieuof using the entire server database 543. For example, the local database643 need only to store the parameters that the terminal would require tocalculate (on the terminal 410) which channels (if any) can be used totransmit towards a given intended receiver (e.g., satellite) 420 from aspecific GPS location without interfering with any incumbent receiver(e.g., PtPR) 310. To achieve this, a system in accordance with theembodiments herein may introduce the use of major and minor horizons,which provide a representation of the more complex description of areas2110 within the protection zone which have a line of sight to theincumbent receiver as viewed from an incumbent receiver (and projectedonto link budget derived boundary polygons 1700). This representationmethod reduces the amount of stored data on the terminal (e.g., as wellas the time/bandwidth required to synchronize the local database 643with any updates to the FCC database and/or the server database 543), asdescribed below.

Specifically, rather than maintain the topographic information in themobile device and calculating the visible protection zones 2110 ormaintaining a list of all of the out-of-sight portions of the protectionzones 1700 which could be excluded from the protected zone, one or moreembodiments of the techniques herein simplify the data structure storedon the terminal by maintaining only the farthest locations (“horizons”)in the protected zone 1700 (or, as mentioned above, simplified zone1400), from which there is still a line of sight towards the incumbentreceiver 310.

FIG. 22 illustrates the reduced protection zone 2110 of FIG. 21, alongwith an associated major horizon 2220 and minor horizon 2230, associatedwith incumbent receiver 310 as described herein. To calculate the majorhorizon 2220, the server 450 may determine the farthest distance withinan arc (e.g., +/−30 degrees), related to the azimuth of the specificincumbent receiver antenna, from which there is still a line of sighttowards the specific incumbent receiver and from which the link budgetis greater or equal to the noise level threshold as discussed above.Note that the illustrative +/−30-degree section was chosen empirically(arbitrarily) based on the typical shape of the protection zones1700/2110, and other angular ranges may be used to define the arc of themajor horizon (e.g., +/−10 degrees, +/−45 degrees, and so on), so longas the resultant major horizon (angular range and distance), and minorhorizon (described below), would include all of the areas 2110 where atransmission by terminal 410 may interfere with a correspondingincumbent receiver.

Note further that the angular range of the major horizon (e.g., +/−30degrees) may be consistent across all incumbent receivers (e.g.,receiver A having a major horizon with distance X and a receiver Bhaving a major horizon with distance Y, where both angular ranges of themajor horizons are a pre-defined +/−30 degrees), or else may bedifferent and defined on a per-receiver basis (e.g., receiver A having amajor horizon with distance X and a determined angular range of +/−30degrees, and a receiver B having a major horizon with distance Y and adetermined angular range of +/−20 degrees). Note that in such anembodiment, the different angular ranges for the arcs of the majorhorizons would thus need to be also transmitted to and stored within thelocal database 643 of the terminals (e.g., in the above example, thelocal database 643 would need to store the +/−30 degrees for receiver A,+/−20 degrees for receiver B, etc.).

The major horizon 2220 is illustratively marked within FIG. 22 as a“pie-shaped” section which spans 60 (+/−30) degrees, having a radius(distance from the incumbent receiver 310) being defined by the majorhorizon. As can be seen, all of the visible (black) locations 2110 fromwhich there is line of sight towards the incumbent receiver within the+/−30-degree section (and that are in the protection zone 1700, i.e.,defining the locations where a terminal's transmission may interfere)are located within the arc of the major horizon 2220 (that is, thepie-shaped section).

Similarly, the system may also determine the farthest locations in theremaining 300 degrees (or whichever remaining portion of the 360 degreessurrounding the incumbent receiver) which are in the protection zone1700, and particularly from which there is a line of sight (reducedzones 2110). This distance is defined to be the minor horizon 2230,which, as shown in FIG. 22, defines an arc that generally surrounds anyremaining visible side lobes or back lobes of the incumbent receiverwhich is not already encompassed by the major horizon. It should beagain noted that according to this embodiment, all of the areas 2110within the protected zone 1700, from which there is a line of sighttowards the incumbent receiver, are included either in the major horizon2220 or within the minor horizon 2230.

According to this particular embodiment of the techniques herein,therefore, an illustrative local database 643 on the terminal wouldinclude the following information for each incumbent receiver 310: index(tower ID), tower latitude and longitude, antenna azimuth, polarity(horizontal and/or vertical), satellite transponder channels that theincumbent receiver frequencies overlap, and major and minor horizons(e.g., for each intended receiver/satellite, and for eachazimuth/elevation smear value as described above). (Also, for satellitereceivers, which may have an assumed altitude of 22,336 miles, an angleof elevation of the receiver (with relation to the terminal, e.g.,calculated based on the position of the satellite in the sky and the GPSlocation of the terminal) may also need to be known for correspondingcalculations, as mentioned herein.) Illustratively, the databaseconsists of approximately 17 bytes of data per incumbent receiver. Thespecific size (number of bytes) of a terminal's local database 643depends on the number of parameters stored for each incumbent receiver.For example, some antennas operate in only horizontal or verticalpolarity while other may operate simultaneously in both horizontal andvertical polarity. As such, in one possible embodiment herein, if anincumbent receiver has a dual polarization antenna, the techniquesherein may be configured to assume the worst case and use only a single(i.e., the longest) horizon. Alternatively, if the antenna has only asingle polarity, then the database may be populated with two differenthorizons in this embodiment, one for transmitting in a polarity alignedwith the incumbent receiver's polarization, and the other oneperpendicular to the receiver's polarity.

Now that the server's database 543 has been populated with arepresentation of a potential interference zone, particularly selectedfrom one or more of the simple protection zones 1400 link-budget-basedprotection zones 1700, or, preferably, the major and minorrepresentations 2220/2230, as described above, this information may thenbe shared with the terminal 410 for storage in its local database 643.In accordance with one or more embodiments herein, the terminal 410 maybe configured to receive the information for its database 643 in avariety of manners.

First, with regard to communication of the data, the data about theincumbent network may illustratively be uploaded to the terminal 410during initial configuration of the device (e.g., by the manufacturer),and/or when high-bandwidth connectivity (e.g., Wi-Fi, USB connection toan Internet-connected device, cellular, etc.) is available. Retrievingthe data over a lower bandwidth connection, such as a satellite link,might take a long time, and as such, an illustrative (and non-limiting)embodiment reserves such low-bandwidth link transfers for smallerupdates or emergency downloads only.

In particular, with regard to updates to the data, the techniques hereinmay preferably ensure that the terminal databases are kept updated atall times in order to properly account for any changes to the incumbentsystem's configuration (e.g., new or changed licenses, etc.). Note thatupdates to the underlying information of the incumbent network may occurmonthly, weekly, daily, multiple times per day, or at any intervaldetermined by the system. The terminals 410 herein may thus beconfigured to synchronize with the latest server database 543 (i.e.,check if it is up-to-date). In one aspect of the techniques herein, theterminals 410 may be configured to regularly synchronize and update (ifout-of-date/sync) their local database whenever connected to ahigh-bandwidth link, or otherwise so long as the terminal is able tocommunicate with the server (or some other system infrastructure) via anetwork that does not need to avoid interference with incumbentreceivers. For instance, this may occur while a user is at home (e.g.,preparing for a trip), or else in the field whenever a wireless network(e.g., Wi-Fi, cellular, etc.) becomes available. In another aspect ofthe techniques herein, particularly in embodiments with zerointerference tolerance, the terminals must confirm that their localdatabase is up-to-date/synchronized with any updated information aboutincumbent receivers (e.g., at least local receivers) when the terminaldesires to transmit. In this aspect, should the local database beout-of-date, then any downloads at this point (e.g., on thereduced-bandwidth satellite channel) may be limited to a relativelysmall region around the present location of the terminal.

Regarding what, exactly, the data is that is downloaded to the terminal,various embodiments are presented herein, ranging from a full download(all of the information for the entire incumbent network), down to aminimalistic download (e.g., update) of data related to incumbentreceivers in the vicinity of the terminal 410. In particular, since ageneral embodiment of a terminal 410 assumes that storage of informationabout the entire incumbent network (and terrain information, etc.) maybe too large for the terminal's memory (and/or processing) capacity,various storage efficiencies may be considered herein. That is, thoughthe storage and computation requirement of the database 643 andprocessor 620 of device 410 may be reduced greatly by the simplifiedmajor and minor horizons representation of the protection zones, thissimplified database representation may still be too large (and timeconsuming) for updates over a low-bandwidth satellite communicationchannel 400. To alleviate this problem, the database may be furtherdivided into geographical zones, wherein each zone contains only partialinformation of the whole database.

For instance, in one embodiment, the data used to update the database643 of terminal 410 is limited to whatever portion (zones) of theincumbent network that is deemed applicable, e.g., based on location ofthe terminal (e.g., if the terminal is located in the western portion ofthe United States, only information about incumbent receivers in thewestern portion of the United States, as opposed to all incumbentreceivers in the United States, may be used to update the database ofthat terminal). Note that the use of western and eastern regions ismerely one illustrative embodiment, and any number of regions or“geo-zones” (or zones) may be established, such as based on the size ofthe resultant per-zone “sub-database” (e.g., to balance the number ofincumbent receivers in each zone), or other factors deemed appropriate.In one illustrative (and non-limiting) example, fourteen (14) geo-zonesmay be used to divide the incumbent network of PtPRs in the UnitedStates into manageable portions (note that the geo-zones may overlap).

In another embodiment, various levels of detail may be downloaded to theterminal, such as, for example, detailed (precise) information regardingall incumbent receivers communicating only on certain frequencybands/channels (e.g., hailing channels, described below) within theentire incumbent network (e.g., link-budget-based protection zones1700/1700+), major and minor horizon information protection zones(2220/2230) for a given geo-zone region (e.g., California), and thendetailed terrain information (2010) for a sub-region (e.g., the hillswithin 50 miles of Palo Alto, Calif.). Any combination of informationgranularity and coverage may be conceived, and the present disclosure isnot limited to only those mentioned herein. In addition, the differentlevels of information may also be time-dependent, meaning generalinformation may first be downloaded, and then as the terminal attemptsto transmit from a given location or moves around to differenttransmission locations, then depending upon the level of availablebandwidth on the communication medium, additional information may besupplemented while “in the field”. (For example, as described below, a“hailing channel” may be used to initiate communication, and then forthis currently mentioned embodiment, that initial communication could beused to supplement additional information to the terminal to assist indeciding the particular channel to use for the remainder of thecommunication.)

Armed with the appropriate information about the incumbent network 300,the terminals 410 may proceed to transmit safely (without interfering)according to the terminal-based operations described herein. (See,again, the general description above in FIG. 12B.) In particular, aterminal 410 (e.g., attached to a smartphone, within a smartphone, or asa part or accessory to any other device with a primary communicationchannel, such as cellular, Wi-Fi, etc.) may first turn on itspotentially interfering communication process (e.g., satellite-basedcommunication in the C-band). In one embodiment, this may be a simpleon/off functionality, or else in another embodiment may be based onwhether the primary communication channel lacks sufficient coverage.

Once on, or once otherwise ready to attempt transmission, the terminal410 must determine its geographical location within the incumbentnetwork. Generally, the level of accuracy of a satellite-based globalpositioning system (GPS) is preferred, though other known locationtechniques may be used. (Note that for reduced accuracy locations,including GPS location inaccuracies, additional safeguards may beutilized, such as expanded location possibility calculations, reducedcommunication power, designated/reserved channel usage only, etc.) Forexample, due to limitations of GPS systems, the location of the terminal410 may not be determined with complete certainty, so the putativecoordinates of the terminal may be insufficient to guarantee thattransmission is allowed. (Certain GPS software provides not onlycoordinates but an uncertainty distance d_uncertain, such that themobile device is assumed to be found within a circle of radiusd_uncertain around the reported location (latitude/longitude).) Notethat in addition, the techniques herein, in certain embodiments (e.g.,adhering to FCC requirements), may also determine the distance that canbe traveled from the current location, so that transmission occurringwhile the terminal is in motion can be performed without moving into ainterfering protection zone (that is, for example, while moving in acar, on a boat, on a drone, etc.).

With its current location information, the terminal 410 may then proceedto ensure that its transmission will not interfere with an incumbentsystem 300 (e.g., ensuring that it complies with FCC rulings and neverinterferes with any of the incumbent PtPRs). In particular, for thecurrent terminal location (e.g., any and all positions within anuncertain circle mentioned above, or any position potentially reachedwhile in motion), the terminal references its database 643 to determinewhether the location is within a protection zone (simplified zone 1400,link-budget-based zone 1700, smeared zone 1700+, major/minor horizons2220/2230, and so on) of any incumbent receivers 310, as detailed above.

Recall, as described above, that a protection zone for a receiver 310(e.g., PtPR) is the geographical area around the receiver (asdetermined/defined by the server 450) in which a transmitting terminalmight add an unacceptable amount of noise to that receiver. For example,PtPRs are sensitive to a terminal that is transmitting on a frequencywhose bandwidth (e.g., +/−4 MHz) overlaps the frequency band of thePtPR. The chance for a terminal's transmission to interfere with anincumbent receiver 310 is a function of the incumbent receiver's antennacharacteristics and that antenna's orientation relative to theterminal's location, the transmission power of the terminal antennarelative to the incumbent receiver location, and the distance betweenthe terminal and the incumbent receiver, and so on. Recall, also, thatthe server 450 may be configured to provide simplified but less-precise(and more conservative) representations of the protection zones to theterminals (e.g., simplified protection zones 1400, major/minor horizons2220/2230, etc.), in order to save resources of the terminals.

According to the techniques herein, therefore, rather than merely takinga generalized protection zone as a simple go/no-go indication of anability to transmit (one optional, though imprecise embodiment herein),when the terminal 410 detects that a potential for interference exists(i.e., that the location is within a protection zone of a specificincumbent receiver), the terminal may then specifically determinewhether any chance of interference would actually occur based onreal-time link budget calculations from the precise location of theterminal towards this specific incumbent receiver.

In particular, according to one or more embodiments herein, for each oneof the incumbent receivers having a protection zone within which theterminal's location resides, the terminal may calculate the link budgetfrom the current location to the incumbent receiver, and may determinewhether transmission from that location would interfere with operationsof the unintended receiver (that is, whether the transmission wouldsurpass a noise floor of the unintended receiver, optionally plus anadditional safety margin, e.g., 6 dB). If it would (or would possibly)interfere, then that particular communication configuration (e.g., aparticular channel to a particular receiver/satellite, at a particularpolarity, etc.) may be deemed unavailable for transmission by theterminal in that location. Otherwise, the communication configuration isavailable to transmit without interfering with the incumbent network300.

Note that this calculation takes into account the transmitterproperties, such as pointing towards a given intended receiver (e.g.,satellite) 420. For instance, in one embodiment, a terminal may firstcheck a default communication configuration, e.g., a particular channelto a particular receiver/satellite, and as such, would compute the linkbudget for that particular receiver/satellite. In another embodiment,however, the terminal may first check all possible communicationconfigurations (e.g., different channels, different intended receivers,etc.) to determine whether any channels are freely available (i.e., thatdo not need a link budget calculation). In this instance, if no channelsare freely available, then the terminal may compute the link budget forany one or more of the communication configurations (e.g., differentchannels, different intended receivers, etc.), and may select oneparticular channel on which to transmit, as described below. (It is ofcourse possible that in some cases there are no protection zonescovering the location of terminal 410, and in such a case, link budgetcomputations may not be necessary, and the terminal may simply transmitfreely without fear of inducing interference.)

In one or more embodiments herein, in order to further ensureeliminating the prospect of interfering with an incumbent receiver, thelink budget calculation performed by the terminal 410 may also take intoaccount any uncertainty in any parameter used to calculate the linkbudget, such as measuring the direction (azimuth and elevation) in whichthe terminal points (e.g., similar to the smearing operation performedin the ground station/server as described above), or the uncertainty ofthe GPS location, such as uncertainty specifically reported by the GPSsystem of the terminal. For instance, regardless of the smearing orother expansion to protection zones as described above, the link budgetcomputation by the terminal is based on whether it is within aprotection zone, and the link budget computation itself thus returns toa level of mathematical precision according to various assumptions ofthe physical properties of the terminal at any given moment. However,for the same reasons as described above (inaccuracy in location orazimuth, shaking hands, etc.), this extra level of assurance may bebeneficial to re-include into the link budget computation in order toaccount for such variations in actual transmission properties in orderto ensure that under no circumstances the terminal 410 would interferewith incumbent receivers 310.

Other considerations, such as line-of-sight, may also be used todetermine the chance of interference. For instance, as described above,since certain communication frequencies (e.g., C-band) need a clear pathto the receiver, granting the terminal a permission to transmit alsodepends on whether or not there is a clear line-of-sight between theterminal and the unintended receiver (i.e., whether the terrain betweenthe receiver and prospectively transmitting terminal would block thetransmission in the direction of the receiver). In embodiments where theterminal has terrain information, further limitations may be placed on(or removed from) the possibility of interference with an incumbentreceiver, since there will be defined regions within which a terminalwould not be visible to, and would thus not actually interfere with, theincumbent receiver, regardless of what the link budget calculationsabove would otherwise assume. That is, even if the link budgetcalculation might indicate an interfering location, the fact that theunintended receiver would be topologically blocked from the transmittingterminal would render communication from that location available. Notethat in one embodiment the link budget calculation may be performedfirst, and then terrain-based limiting may be performed to furtherfilter the results of the interfering regions. Alternatively,terrain-based limiting may first be performed to filter the areas withinthe approximated protection zone for which a link-budget calculationwould be necessary (e.g., if an unintended receiver is blocked for aparticular region within which the terminal is located, there would beno need to perform a link budget calculation for that particularreceiver).

Notably, the techniques described herein may make the choice offrequency diversity, satellite diversity, or polarization diversity byselecting the minimal potential for harmful interference, e.g., based onthe particular location of the terminal 410 at the time it desires totransmit. As described above, frequency diversity is one way to avoidinterference on one frequency by moving to another frequency for whichthe terminal would not be within a protection zone.

FIGS. 23A-23B, for example, illustrate a geo-locational example ofavoiding interference in wireless communications in accordance with thetechniques herein. For instance, in the geographical visualization 2300of FIG. 23A, assume that there are five receivers 310, A, B, C, D, andE, within the proximity of a potentially transmitting terminal 410. Asshown in FIG. 23A, three of receivers, A, B, and C are configured toreceive on an illustrative channel “1” (a given frequency band), andtheir respective protection zones 2350 are shown. As can be seen,terminal 410 attempting to transmit to a specific intended receiver(e.g., satellite) 420 falls within the protection zone of receiver C onchannel 1, and, assuming either that protection zones 2350 (e.g., simpleprotection zones 1400, link-budget-based protection zones 1700, or themajor and minor representations 2220/2230) are dictating go/no-goauthorities, or else assuming that a link budget calculation to receiverC determines that a transmission on the incumbent receiver's channel 1would interfere, the system described herein would determine thatchannel 1, at that current location of terminal 410, is unavailable fortransmission towards the intended receiver.

Conversely, as shown in visualization 2310 of FIG. 23B, assume thatreceivers D and E are configured for an illustrative channel “2” (adifferent frequency band than channel 1 above), and that protectionzones 2350 of those receivers either do not overlap with the location ofthe terminal, or else the link budget calculation determines thatcommunicating on channel 2 would be acceptable (non-interfering) withany incumbent receivers (e.g., PtPRs). In this instance, the terminal410 would be permitted to transmit on non-interfering channel 2 towardsthe intended receiver (e.g., satellite) 420, but not permitted totransmit towards that intended receiver (e.g., satellite) on theinterfering channel 1. Note that the views shown in FIGS. 23A-23B arevastly simplified from real-world examples, and are meant solely as anillustration, and are not meant to be limiting to the scope of thetechniques herein.

In addition to frequency diversity, there are several additionalcommunication configurations that can be adjusted to avoid any risk ofinterfering as well. For instance, in addition to frequency diversity,there are also satellite (or orientation) diversity and polarizationdiversity. Polarization diversity involves switching to the oppositeantenna diversity to reduce interference. For example, certain terminalconfigurations may be able to transmit with either horizontal orvertical polarity, switchable on demand, or else by instructing a userto rotate the terminal to a different polarity. When the unintendedreceiver's antenna utilizes the same polarity as the terminal'stransmitted signal, the distance from the incumbent receiver wherecommunication is safe is quite a bit farther than when the transmitterand incumbent receiver polarities are not the same. The techniquesherein may also account for various considerations for when one or bothof the intended and unintended receivers may operate in dual polarities,particularly in a manner that reduces interference at the unintendedreceiver.

In FIGS. 24A-24B, an example of choosing satellite diversity is shown.Here, for example, a switch from a western satellite (e.g., 193-degreeazimuth to the illustrative Galaxy 12 satellite) to an eastern satellite(e.g., 142-degree azimuth to the illustrative Galaxy 3C satellite),while remaining on the same channel, can be confidently computed byusing the antenna gain parameters of both the unintended receiverantenna (Gr) and the gain of the terminals' transmitting antenna (Gt).For example, assume that as shown in FIG. 24A the terminal 410 considersa transmission to the western satellite (while at a location that isillustratively 9 degrees off of the incumbent receiver's bore-sight). Inthis position, and based on the corresponding aiming direction of theterminal's antenna for transmission to the western satellite, theterminal 410 falls within the protection zone 2350 of one particularincumbent receiver 310. Assume, for this example, that after perform thelink budget calculations above, the terminal determines that atransmission from this location to the western satellite would(potentially) interfere with the operation of this incumbent receiver(the received power at the incumbent receiver would be above the noisefloor), and would thus prohibit transmission under these parameters.

In FIG. 24B, on the other hand, when communicating with the alternativeeastern satellite (e.g., 142-degree azimuth to Galaxy 3C), thus pointingslightly away from the incumbent receiver at issue, a correspondingprotection zone 2350 may change based on the new angular relationship ofthe transmitter and incumbent receiver, since the link budgetcalculation to the incumbent receiver takes the aimed direction(transmission lobe) of the terminal's antenna into account. Note thatwhile the satellite diversity switch may result in the terminal nolonger being located within a protection zone 2350, at which time nofurther analysis would be necessary (i.e., the terminal would be free totransmit to that alternative satellite), the terminal 410 in thisexample may be still illustratively located within protection zone 2350,which still requires additional detailed analysis. According to the newaimed direction of the terminal's potential transmission, assume that itmay now be determined (e.g., based on a link budget calculation) thatthe received power at the incumbent receiver would be below the noisefloor, and as such, the transmitter would be allowed to transmit to thealternative satellite, unlike when transmitting toward the westernsatellite in FIG. 24A above from the same location. Thus, by usingintended receiver (e.g., satellite) diversity, additional communicationconfigurations may be achieved that offer more available options for asuccessful (i.e., non-interfering) transmission.

Note that where multiple communication configurations are available fortransmission (i.e., without introducing any interference at anyunintended receivers), the techniques herein may provide variousconsiderations to allow the terminal 410 to select a specificconfiguration, and to proceed with its communication to the intendedrecipient (e.g., satellite) 420. For instance, the configuration (e.g.,channel, recipient, polarity, transmission power, etc.) may be selectedeither a) in a manner that maximizes the link budget towards theintended receiver (e.g., one of the satellites), b) in a random wayamongst the entire available set of configurations for the terminal tocommunicate with a specific receiver (e.g., a specific satellite), c) ina random way amongst the entire available set of configurations for theterminal to communicate with all of the available receivers (e.g., allof the available satellites), or d) in a manner that load balances anygiven channel's use across a plurality of terminals (e.g., based onserver participation).

Conversely, should no communication configurations be available fortransmission, regardless of communication diversity options discussedabove, then the techniques herein prevent transmission from the terminalin order to avoid interference with the incumbent system 300. Note,however, that various additional measures may be attempted by theterminal prior to completely ruling out any communication from itscurrent location. In particular, the techniques herein also provide forvarious considerations for controlling an expected receive power at anincumbent receiver 310. For example, in one embodiment, if it isdetermined that the terminal 410 is in a location where the link budgetis only marginally over a pre-determined threshold, thus indicating thatterminal 410 is prohibited from transmitting towards a specific intendedreceiver (e.g., satellite) because it would interfere (albeitmarginally) with a given unintended incumbent receiver (e.g., PtPR) 310,the terminal may be configured reduce the power encountered by theunintended receiver (e.g., PtPR), and as such render a location whichwas marginally in a protected zone to become an unprotected transmissionlocation for that particular channel.

According to one or more embodiments herein, such a reduction of receivepower at the unintended receiver may be based on reducing the transmitpower of the transmitter, that is, attempting to transmit at less thanthe nominal power on a given channel. To accomplish this, the terminal410 may first calculate a reduced transmission power that would notcause any interference with the incumbent receiver (e.g., PtPR) 310. Theterminal 410 may then calculate the link budget with this reducedtransmission power towards the intended receiver (e.g., satellite) 420.If the link budget, using the reduced power, is greater than thesensitivity of the intended receiver (while still not interfering withthe unintended incumbent receiver), the terminal 410 is then allowed(e.g., granted the permission) to use the given channel at a reducedpower. Alternatively, the device may compare the amount of power it isover the noise floor of the unintended receiver, Delta PU, against theamount of power it is over the sensitivity of the intended receiver,Delta PI. If Delta PI is greater than Delta PU, then the receiver mayreduce its transmission power by Delta PU as to reduce the receivedpower at the unintended receiver below the required threshold whilemaintaining adequate power level (above receiver sensitivity) at theintended receiver.

Note that in one or more additional embodiments herein, the transmitpower from the terminal 410 may also be selected for other reasons, suchas based on an ability to transmit at reduced power while still meetingthe link budget at the intended receiver 420, e.g., to save/extendbattery life. That is, the transmission power may be based on the linkbudget calculations described above ahead of the transmission (or elsebased on a measure of receive power at the intended receiver, i.e., afeedback-based control). Further, such reduced transmit power may be inthe form of a non-linear duration representation to save on transmissionbandwidth.

As an alternative to explicit transmission power reduction, othermeasures may be taken to reduce the receive power at the unintendedreceiver, such as changing the azimuth, elevation, and/or elevationangle of the transmitter. In particular, by varying the physicalorientation or placement of the terminal's transmitting antenna 660,such modifications may have the effect of improving the link budgetcalculation to the unintended incumbent receivers. This concept wasdescribed generally above with reference to satellite diversity (FIGS.24A-24B above), where changing the angle away from an incumbent receiverfrom one satellite to another could create a situation where atransmission would be allowed. Here, however, the concept is the same,but rather than switching, for example, from the western satellite tothe eastern satellite, imagine now that the terminal (or user holdingthe terminal) is instructed to aim the terminal's satellite 660 in aposition that is even further east (e.g., up to 20 degrees beyond theillustrative 142-degree azimuth, say 122 degrees), e.g., for theduration of the communication session or only for the duration that thedevice is transmitting. In this manner, though the receive power at theintended receiver (e.g., the eastern satellite) may be reduced by theoff-center aim, the receive power at the unintended incumbent receivermay be reduced to a level that no longer interferes (e.g., based onadditional link budget calculations according to the updated transmitterorientation). As such, the techniques herein provide various physicalorientation provisions (e.g., instructions, control of automatedactuators, etc.) to re-orient the transmitter in a manner that reducesthe receive power at the unintended receiver. Some illustrative examplesof such re-orientation may include, among others: a higher elevationangle; further away from the unintended receiver; at an azimuth awayfrom the unintended receiver (and possibly away from the intendedreceiver as well); at an azimuth slightly different than towards theintended receiver (and away from the direction towards the unintendedreceiver); at a rolled pitch (e.g., sideways) in order to reduce thereceived power at the unintended receiver by misaligning thepolarization of the transmitted signal with the unintended receiver;moved to a higher elevation (e.g., climbing a hill, elevating a drone);or possibly even to a lower elevation (e.g., removing the terminal fromthe line-of-sight of the unintended receiver); and so on.

Other options for reducing the interfering receive power may beavailable, and any combination of the above options may be suitable aswell. It should also be noted that in any of the above cases, the system(e.g., terminal and/or server) verifies that the reduction of linkbudget towards the unintended receiver (e.g., PtPR) 310 maintainssufficient link budget from the terminal 410 towards the intendedreceiver (e.g., satellite) 420. In addition, transmissions (e.g.,packets) sent at a reduced power (or alternate orientation) may bemarked accordingly to make the ground station aware that a reduced power(or orientation) is used from a protected area from which transmissionwith nominal power (at an expected orientation) is prohibited.Furthermore, it is important to note that certain of these above actionsmay also affect the link budget in the direction from the intendedreceiver (e.g., satellite) as a transmitter back towards the terminal410 as the receiver (i.e., the downlink direction), and care andinstruction should also be taken to remain within the proper receptionconditions for the intended communication in both directions (ifnecessary).

Notably, should the intersection of protection zones in any given areabe covered on each channel/frequency for which the terminal 410 isconfigured to transmit, or, more specifically, if the link budgetcalculations at the terminal confirm that any possible communicationconfiguration (channel, power, direction, etc.) would interfere with atleast one incumbent receiver, then such an area is a protected or“blocked” area, and no transmission would be allowed. Said differently,a protected/blocked area is a geographical area in which none of theselected transponder frequencies can be used to transmit from theterminal 410 to its intended receiver (e.g., the satellite 420). Thatis, a transponder frequency can only be used if the transponder liesoutside of the interference levels (e.g., protection zones/link budget)of all receivers whose frequency range overlaps the transponders'frequency range, and a terminal is determined to be within a protectedor blocked area if it is in the protection zone of at least one receiver310 (e.g., PtPR) for each of the available transponder frequencies.(Notably, with the illustrative example communications systems andfrequencies as mentioned below, such areas are considered to correspondto less than 0.001% of the United States' geographical area.)

According to one or more embodiments of the present disclosure, thetechniques described herein may be based on a centralized model, alocalized model, or some other model in between. For instance, accordingto an illustrative centralized model of operation, a local terminal 410may provide its location information to a centralized system (server450) on a first cleared channel (e.g., a hailing channel that iscomputed to not interfere, or that is known to never interfere),illustratively via the satellite link 420, and the centralized systemperforms computations and reports back to the mobile transmitter a setof one or more potentially interfering channels (e.g., communicationchannels) on which the transmitter (terminal 410) is allowed to transmitfrom that particular location (i.e., that do not interfere). Inlocalized embodiments, information about the local incumbent wirelesscommunication system 300 may be loaded in the terminal 410 from theserver 450 (e.g., when connected over a higher speed network), and theterminal may perform the computations and determine, for itself,acceptability of transmitting on potentially interfering channels. Evenin such localized embodiments, periodic updates and permission-basedconfirmation/validation may be required before the terminal is allowedto transmit. That is, a permission-based operation can be used to shutdown terminal communication if necessary. (Note also that in thepreferred embodiment, no earth terminal will transmit until itsynchronizes with the spread spectrum signal that a satellite transmits.That is, the satellites 420 may be configured to send out a regular,repeating broadcast on a non-interfering downlink channel (e.g., 3702.5MHz or other pre-arranged frequency bands). This broadcast may, amongother things, provide frequency and timing symbols to decode the directsequence spread spectrum signal for forward path communications, as wellas indicating database updates/versions in order to allow a terminal todetermine whether its local database is up-to-date before transmitting.)

In order to effectuate the centralized and/or local (permission-based)modes mentioned above, the techniques herein may provide for one or more“hailing” frequency bands/channels, which as described below, aregenerally consistent in configuration (few updates), and have minimalregions of potential interference (sparsely assigned).

In particular, using the illustrative embodiment as an example,satellite transponder channels may be defined by a center frequency, awidth, and polarity. Each satellite may have any number of the same ordifferent transponder frequencies that one can communicate with. Asnoted above, some of these transponder frequencies may lie in areas ofthe C-band spectrum where the FCC will likely allocate very few (if anyat all) frequencies to be used by PtPRs in the future, and the rest maylie in frequencies where any number of changes may occur on a dailybasis. The techniques herein propose to assign these specific channelsthat have the perceived minimal potential for additions or changes asthe hailing frequency channels (or hailing channels). It should be notedthat while areas of the C-Band spectrum have been identified where itcan be assumed that few, if any, changes will occur in the future, thetechniques herein may also have the ability to use transponder channelsin areas of the C-band spectrum where many changes may occur.

Currently, in the entire United States and its territories, of the56,000 PtPRs in use, there are approximately 61 PtPRs whose frequencyand width overlap the frequency range of 6168-6182 MHz, andapproximately 18 PtPRs whose frequency and width overlap the frequencyrange 5925-5930 MHz (as opposed to an example of thousands of PtPRswhose frequency channel overlaps any arbitrary 8 MHz wide bandwidthchannel in the 5930-6168 and 6182-6425 MHz range). Per FCC regulations,it is currently expected that the FCC will issue few new licenses to usethese hailing channels on any new or old PtPRs. However, the existingPtPRs which utilize frequencies and widths that overlap the hailingchannels are grandfathered in with permission to continue using thesechannels. Accordingly, these two frequency ranges, 5925-5930 MHz and6168-6182 MHz, may be selected for use as the hailingfrequencies/channels herein. (Note that in the 6168 to 6182 MHzspectrum, new allocations are currently limited to 3.75 MHz or less,which prevents the allocation of a single frequency at a location fromconsuming the entire 14 Mhz spectrum width.)

In one example implementation, the hailing channel has a bandwidth of 4MHz (a half-width channel) but nothing restricts the hailing channel to4 MHz. The 4 MHz bandwidth was selected because it fits within the5925-5930 band, and similarly three total hailing frequency channels of4 MHz can fit within the 6168-6182 band. The half-width 5927.5frequency, at the center frequency of the 5925-5930 MHz segment of theC-band, may be illustratively chosen as the primary hailing channelbecause there are only 18 PtPRs in the United States on this frequency(between 5925.1 and 5930 MHz), which provides a very high coverage rateas a low-bandwidth, lightly-used channel. Of course, these 18 PtPRs muststill be avoided when a terminal is in the Protection Zone of one ofthese specific receivers. As such, the terminals in this illustrativeembodiment initially contain the records of all 18 Hailing FrequencyPtPRs, which may be updated whenever they change.

FIG. 25A illustrates an example table 2500 of active point-to-pointmicrowave links between 5925.01 MHz and 5930.0 MHz in the United States.Note that from the northern hemisphere to communicate with ageostationary satellite, a terminal must be pointed in a southerlydirection to the equatorial plane, where the geostationary satellitesreside. As can be seen from the table 2500, of these 18 links, onlyeight have receivers that point in a northerly direction. Thus, if thePtPR protection zone points south, the resultant protection zone(s)would be smaller than northerly facing PtPR protection zones. Asimplified illustration of this is shown in FIG. 25B, with northerlyfacing zone 2510 being larger than southerly facing zone 2520.

Notably, in the illustrative example, each satellite has n full-width (8MHz) channels. From initial analysis, using different channels on eachsatellite gives maximum coverage for the minimum number of channels—forinstance, simply using 5934 MHz and 5998 MHz on Galaxy 12 and 5974 MHzand 6030 MHz on Galaxy 3C (in addition to the hailing frequency on both)yields 99.999% coverage of the US (including Hawaii and Alaska). Fullanalysis may be used to determine the optimum/minimum channel selectionto produce the largest unblocked area overall, and the examplefrequencies and configurations herein are merely representative examplesof generally large coverage areas. Note also that this assumes usingonly two satellites and only two channels per satellite (e.g., inaddition to the illustrative 5927.5 MHz hailing frequency on eachsatellite), but more than two satellites and channels may be availableand may be accounted for.

In general, given that the illustrative embodiments above forcentralized and/or localized communication may use the hailingfrequencies as an initial part of the communication with satellite(e.g., to confirm or determine the actual channel to use for thefollowing transmission) for all terminals 410 in the network 400,techniques herein attempt to minimize the use of the hailingfrequencies, such as for only the initial signaling as mentioned above(e.g., permission, channel selection for the primary transmission, andso on). In one or more particular embodiments, however, the hailingfrequency bands/channels may be made available with limited use forterminals that are blocked from transmitting on the other (non-hailing)channels, such as due to the proximity to a PtPR with an overlappingfrequency. In this regard, the techniques herein may allow for certaincommunication capability on hailing channel, such as in response to aterminal that can communicate with a satellite only via a hailingchannel. In such an instance, with no other option, the terminal may beconfigured to either use the hailing channel as the selected channel, ormay use the hailing channel for a limited amount of data (or bandwidth,e.g., data/time), such as by limiting the length of messages sent.Preferably, in one embodiment, the terminal 410 may only use the hailingfrequency for its communication based on first receiving serverpermission, or else once a user has acknowledged that it is an emergencycondition (e.g., to limit over-use of the channel simply because noconventional channels are available at the current location). (Note thatin certain embodiments, in such a situation, the terminal may provide orbe provided with navigational guidance to move the terminal to a placewhere additional communication channels may be available.)

Note that there may be circumstances where, within a given region, PtPRprotection zones may change and intersect all return path channelfrequencies (e.g., if the hailing channel(s) have changed for thecurrent zone), such that transmission from that zone is effectivelyblocked, unless a wireless update can be received since the terminalwill have no available return path frequencies to transmit on. To avoidthe terminal from being “locked out” by this occurrence, a pushed-updatemechanism may be provided to broadcast, e.g., from the satellite 420 toterminals 410, any channel changes that have recently occurred (e.g., inthe last 21 days) to the hailing channels. (Note again that in theexample implementation, the downlink channels, e.g., 3702.5 MHz, are notchannels that would interfere within the incumbent PtP system 300, andthus the terminals can freely listen on these channels for updates.)This allows a terminal to determine the availability of an availablehailing channel for the terminal's current zone, so that an incrementaldatabase update can be requested to allow re-evaluating the overall (andup-to-date) channel availability from a current location. This updatemay be broadcast on a separate downlink channel by each satellite, butmay contain information for the available hailing channels for each ofthe satellites. Note that while this does not guarantee thattransmission will be allowed from the current location (if there is alocal intersection with all hailing channels), it does allow update ofthe PtPRs whose frequencies intersect the hailing channels, which thenallows the terminal to transmit once it is moved outside of the localhailing channel intersecting PtPR's protection zone.

Advantageously, the techniques herein provide for avoidance ofinterference in wireless communications. In particular, the techniquesherein enable a mobile communication device (e.g., terminal 410) to knowwhether or not it is permissible to transmit in a particular locationand, if so, on what particular frequency (channel/band) and in whatparticular direction, so as to reduce or eliminate any interference onother communication devices and networks. Additionally, the techniquesherein assist in determining suitable placement and orientation ofterminals for a potentially interfering wireless communication system inthe presence of an existing wireless communication system.

In one specific embodiment, the techniques herein allow (and/or addvalue to) the introduction of a new, ubiquitous service with consumer-and IoT-based applications via satellite (e.g., messaging viasatellite), and make more intensive and efficient use of C-band spectrumthrough a non-interfering sharing regime. The proposed system willprotect other C-band operations from harmful interference—for example,by using a database-driven, permission-based authorization regime toensure no operations cause harmful interference to C-band terrestrialfixed service (“FS”) point-to-point (“PtP”) operations.

Notably, other advantages and additional implementation (use-case)embodiments of techniques described above may be readily apparent tothose skilled in the art, and those specifically mentioned herein arenot meant to limiting to the scope of the present disclosure.

——Magnetic Compass Confirmation——

As detailed above, the techniques herein ensure that a terminal 410 doesnot transmit towards an unintended receiver (e.g., an incumbent PtPR).Specifically, the techniques above detail particular embodimentsregarding how to ensure that a terminal can transmit only when it can beguaranteed that any unintended receiver in its vicinity would notreceive power higher than a given threshold.

Generally, the techniques described above rely on the ability to obtainaccurate reference direction (e.g., to the magnetic north and to thetrue north). Mobile phones 415, such as the phone to which the terminal410 may be attached, have embedded magnetic sensors which can be usedfor determining the direction to the magnetic north (i.e., the pointwhere northern magnetic lines of earth's magnetic field enter the earth,that is, the magnetic field is vertical). The angle between the magneticnorth and the geographic “true” north (the northern endpoint of theearth's axis of spin) is known as magnetic declination, where themagnetic declination depends on the specific geographic location wherethe magnetic sensor measurement is taken. (Note that compass needlestechnically measure the horizontal component of earth's magnetic fieldat a specific location, which due to local anomalies does not alwaysequal the angle to magnetic north, but this minimal deviation may, undersome circumstances, be ignored.)

Additionally, the magnetic poles are constantly moving slowly, and assuch the translation from the magnetic north to the true north is bothlocation and time dependent. For example, a prediction of the currentmagnetic declination for a given location can be obtained online from aweb page operated by the National Geophysical Data Center, a division ofthe National Oceanic and Atmospheric Administration of the UnitedStates. Further, the National Geospatial-Intelligence Agency (NGA)provides source code (e.g., written in C) that is based on the WorldMagnetic Model (WMM), accounting for movement of the magnetic north pole(e.g., adjusted every five years).

A magnetic compass reading is typically accurate, so long as there areno additional magnetic influences. For example such additional magneticinfluences may be introduced by nearby metals, belt buckles, radios,magnets of speakers, backpack metal frames, underground cables or pipes,etc. Any such additional external magnetic fields can potentially causeerroneous direction readings, and as such, may cause positioning theterminal in an erroneous direction. As detailed above, such an erroneousdirection may result in transmission in a wrong direction that couldadversely impact unintended receivers.

The techniques described herein, therefore, provide for magnetic compassconfirmation, in order to ensure that there is no (or at least minimal)magnetic error due to magnetic field interference. In particular, theembodiments described below provide various methods for ensuring thatthe compass, and particularly the direction of an associated mobiledevice, is accurate. For instance, the techniques herein preventtransmission by terminal 410 when there is uncertainty in a compassreading, but may also be used for other technologies wheredirection-related communication needs accuracy and are based on magneticcompass readings.

Specifically, in one preferred embodiment, the present disclosureteaches a method for ensuring that a terminal 410 never transmits in awrong direction. To do that, the system evaluates and determines theaccuracy of the direction reading from its compass, as detailed below.If the system determines that its direction reading is not certain, itmay prevent the terminal from transmitting. (It should be noted that thecontroller prevents the system from transmitting only when accuratebearing/direction is required and the system determines that it does nothave an accurate direction/bearing. In the case when the systemdetermines that it can transmit safely without accuratedirection/bearing, transmission may still be enabled.)

In general, the present disclosure describes a system for determiningwhether the compensated reading of a magnetic sensor is reliable or not.Notably, other systems have been developed that focus on deviationcompensation of magnetic compass systems, such as a system used inaircraft to account for a permanent magnetic field set up by variousmetal parts such as the aircraft engine, or due to the distortion of theearth's magnetic field due to the presence of metal parts which inthemselves do not produce a magnetic field. Still other systems havebeen described for calibration and correction of non-constant compasssensor errors, through changing software and hardware calibration basedon pre-production testing (i.e., improving the accuracy of electronicsensors), or for otherwise reducing power consumption or error of adigital compass. Each of these technologies, however, focuses oncompensating for the distortion of the earth magnetic field. Incontrast, the techniques herein provide a system to assess whether thecompensated reading of the magnetic direction is reliable or not, andparticularly to enable/disable various direction-sensitive features(e.g., transmission from a terminal 410) based on that assessment. (Notefurther that the techniques herein still attempt to compensate for localmagnetic field distortions, but the assessment herein is whether, evenafter the correction and compensation (e.g., for hard and soft iron, aswill be understood by those skilled in the art), that the device is ableto provide accurate directional readings.)

According to one or more embodiments of the present disclosure, thetechniques herein uses two (or more) directional (e.g., magnetic)sensors positioned at a distance from each other (e.g., a smalldistance, dictated by form factor of the device). In one embodiment, thesystem may use an internal directional sensor of the mobile phone 215and one or more additional directional sensors of the terminal 410. Inanother embodiment, the system may have multiple sensors within thephone, or mounted on the terminal, generally as far apart as the systemallows or as otherwise necessary to provide the most benefit to thetechniques described herein.

FIG. 26A illustrates a simplified example of a directionally-sensitivesystem 2600 that has a first directional sensor 2610 and a seconddirectional sensor 2620 located on a same device 2630, in accordancewith one embodiment herein. Illustratively, the device 2630 may be amobile phone 415 attached to a terminal 410, or may be the terminal 410itself (e.g., standalone, or attached to a mobile phone 415). FIG. 26B,on the other hand, illustrates another simplified embodiment of thesystem 2600, where the first sensor 2610 is located on a first device2640, and the second sensor 2620 is located on a second device 2645.Notably these two devices 2640 and 2645 may be physically connected toeach other (e.g., a terminal 410 attached to a mobile phone 415), orelse may be connected via communication only. As noted above, any numberof directional sensors may be used (i.e., two or more), and the viewshown herein is meant for an illustrative example only. Also, thepositioning of the sensors as shown is also illustrative, and anysuitable arrangement, location, orientation, etc., may be used, andconfigured based on a combination of device design, maximizingdifferentiation of sensing, and so on.

Directional sensors 2610 and 2620 may be based on a number of differenttechnologies. Generally, such technologies are designed to sense theearth's magnetic field, such as magnetic sensors (e.g., magnetometers),but other sensors may be used. Magnetic sensors, in general, may beimplemented with different magnetic alignment algorithms and differentsensitivities, and may include such things as Hall Effect sensors (i.e.,a transducer that varies its output voltage in response to a magneticfield), magneto-inductive (MI) sensing magnetometers, and so on. Othersensors, such as GPS sensors (e.g., multiple spread-out GPS sensors, GPSplus direction of travel, etc.), may also be used to determine directionof the sensor (and thus associated device), each with varying degrees ofaccuracy and limitations. The directional sensors herein, therefore, arenot limited to those mentioned herein, and any suitable directionalsensing (or determining) technology may be used, whether magnetic orotherwise.

The impact of an external magnetic field or other magnetic interferencescan vary all the way from a slight error (e.g., a few degrees) to acomplete 180-degree error (if interference is severe enough, such as amagnet placed near a magnetometer). In particular, magnetometers can beimpacted by magnetic fields in their vicinity, where a magnetic field'sstrength is inversely proportional to (d)^3. (That is, proportional toone over distance from the magnetic source to the 3^(rd) power.) As aresult of using at least two different directional sensors 2610 and2620, which would generally be located at a different distance (or atleast a different angle) from an external interfering magnetic source,each would be impacted differently. In other words, the reading of thetwo magnetic sensors would have different distortions (e.g., differenterroneous readings). Note that in one or more embodiments herein, asdescribed below, the techniques may use sensors based on differencetechnologies, and as such, sensors with different sensitivities anddifferent non-linear curves may cause/yield different readout deviationdue to the distorted magnetic field.

As an example, FIG. 27A illustrates an example reading of both sensors2610 and 2620 without interference (e.g., magnetic compass reading),while FIG. 27B illustrates an example reading of the same two sensorsafter an external magnetic source 2710 has been introduced into theenvironment. Assume, for example, that in FIG. 27A, the readings areboth 0-degrees (e.g., magnetic north), without magnetic interference.Once an external magnetic field source 2710 is added in FIG. 27B, ifevery sensor and its associated compensation system is capable ofmitigating the interference, all sensors will continue to give the sameaccurate reading. That is, sensors 2610 and 2620 use magnetometers ofdifferent technologies, and thus the uncompensated readout of themagnetometers are expected to be different because of the differentdistance to the source 2710 and because they use magnetometers ofdifferent technology. Thus, once the system compensates for the soft andhard iron source, if the compensation is successful, then the tworeadouts should be substantially the same, but if the two compensationreadouts are not substantially the same, then there is uncertainty aboutthe direction to the magnetic north. Note, however, that since the twosensors 2610 and 2620 are located at different distances (“d1” and “d2”,respectively) from an external magnetic source 2710, if inaccuratereadings occur, each would exhibit different reading errors and point indifferent directions from true magnetic north (e.g., +5 degrees, and +10degrees, respectively).

Additionally, if the two sensors use different sensing technologies (asexplained above), then the impact of the external magnetic field on thereadings of the two sensors may be further different. For example,though the two magnetic sensors could still point to differentdirections as if they were the true magnetic north, a Hall Effect sensorand a flux-gate effect sensor may exhibit different deviations from thetrue north based on the different sensitivities of the two sensors andthe different non-linearity these technologies exhibit (e.g., +5 degreesand +20 degrees, respectively).

When the system is exposed to only the earth's magnetic field, all ofthe sensors provide identical reading toward the magnetic north. Itshould be noted that as explained above, the bearing towards themagnetic north can be easily translated/converted to the directiontowards the true north using well-known software/methods.

When all of the readings of the various magnetic sensors pointsubstantially in the same direction, the system infers that thedirection reading is correct. The illustrative system above (avoidinginterference) may use this direction to calculate the azimuth in whichthe device (terminal 410) should point to achieve “optimal transmission”(and reception) towards (from) a given intended receiver. That is, foran optimal transmission or reception, using this proper reading, thecontrol software in the terminal enables transmission towards theintended receiver (e.g., satellite 420) while ensuring that the rightfrequency band and polarization are chosen as to ensure that groundcommunication amongst unintended receivers and transmitters is notadversely affected (as described further above).

However, if the directionally-sensitive system 2600 is in the vicinityof objects 2710 that could influence the magnetic field in a way thatthe system is not able to compensate for, then the various differentmagnetic sensors may or may not point towards magnetic north. Accordingto the techniques herein, given the fact that the sensors 2610 and 2620are located at a different locations within the system 2600, and thus adifferent distance (or at least angle) from the source of the adverselyimpacting magnetic field, the impact to each reading is different a)because the sensors are at a different distance from the adverselyimpacting magnetic object (and the impact is inversely proportional tothe distance of the various sensors from the object to the 3^(rd)power), and b) the different sensors may be built based on differenttechnologies have much different sensitivity and non-linearity responseto the disrupting magnetic field, and as such may exhibit differentdeviation from the true north, as mentioned above.

Said differently, two sensors may be used and each attempts tocompensate for the distortion of the magnetic field by an externalmagnetic material or by an external magnet. There may be times, however,where even after the system attempts to compensate for the distortion,there is still a difference in reading between the sensors, and aresultant directional uncertainty (i.e., that the two compensatedsensors give different readouts for the magnetic north). As such, ifthere is external distortion but the system can compensate for it (i.e.,the two readings are substantially similar), then an accurate reading isassumed (e.g., and transmission can be performed). On the other hand, ifafter corrections for the magnetic field distortion are attempted andare not successful (i.e., the two readings are not substantiallysimilar), the techniques herein detect this occurrence (e.g., andprevent transmission).

To illustrate the concerns that being even slightly erroneously aimed,FIGS. 28A-28B demonstrate how a slight angle change might go from notinterfering to interfering. For instance, in FIG. 28A, the terminal 410may be aimed such that the boresight of transmission 405 reaches theintended receiver 420, without interfering with an unintended receiver310. However, with reference to FIG. 28B, a slight shift in antennadirection aim, perhaps due to believing that the device is aimedaccording to FIG. 28A based on an erroneous directional reading (e.g.,of systems with only a single directional sensor), would result in acorrespondingly shifted transmission that might interfere with theunintended receiver 310.

Further, according to one or more embodiments herein, a graphical userinterface (GUI) may be illustrated to a user to adjust aim of theterminal according to the adjusted communication parameters. That is,since the adjusted parameters may require physical orientation changesto the terminal, where the system herein may be configured to preventtransmission by the terminal unless the terminal is aimed correctly,various measures may be taken to guide a user. For instance, theterminal (or a mobile device attached to the terminal) may utilize anembedded (or attached) compass to guide the operator of the mobiledevice to the direction it should point the mobile device (azimuth andelevation, i.e., tilt angle towards the satellite). As such, FIG. 29Aillustrates an example of a GUI 2910 that may be used according to thetechniques described above. In particular, illustrative stationary“crosshairs” 2940 are shown in an augmented reality display to aim at asatellite icon 2950 representing the desired direction to point theterminal (whether the satellite is actually located in that direction,or whether that merely represents the desired “aim” of the terminal toallow the transmission according to the acceptable communicationparameters). Many other types of GUIs and functionalities may beconceived, and those shown herein are not meant to be limiting to thescope of the present disclosure. If the directional sensors areincorrect, however, then the GUI may show an acceptable transmission aimin FIG. 29A (namely, the crosshair icon 2940 coincides with thesatellite icon 2950), when, in reality, the actual aim should look morelike the image in FIG. 29B, wherein the crosshair icon 2940 does notcoincide with the satellite icon 2950, and therefore it is notacceptable to transmit.

As an aside, with regard to antenna pointing (as described above), theterminal transmitter may be activated only when it is within a “safe”shaking angle (e.g., 5 degrees) of the required pointing angle to thesatellite, thus accounting for deviations in aim (e.g., caused byshaking of the terminal, such as from user hand shaking, vehiculartravel, and so on). The terminal uses sensors (e.g., its own or elsefrom an attached smartphone), such as its GPS coordinates and bearing,to enable activation/deactivation of the terminal's transmitter. Aterminal's transmission may be disabled (e.g., within 100 msec) if thepointing angle envelope is ever exceeded. Note that the amount of “safeshaking angle” may be calculated, and the momentary shaking may becontinuously estimated, such that if the shaking may point the antennaof the terminal into an interfering orientation, the user may be alertedand transmission is disabled. The transmission can be quickly enabledagain (and the message transmission resumed) once the terminal ispointing with confidence back to the desired direction. This process isfast enough to permit mobile operation of the terminal for many consumerrecreation activities (e.g., hiking, boating, and horse-back riding)without causing any adverse interference to incumbent receivers such asPtPRs and/or other satellites.

According to the techniques herein, concerns about erroneous directionalsensing (e.g., magnetic compass readings) may be accounted for byconfiguring the two sensors 2610 and 2620 in a manner where the two (ormore) sensors provide substantially different readings when deviatinginterference (which cannot be reliably compensated for) is experienced,such that the system infers that it does not have a reliable directionreading when different (or otherwise conflicting) readings occur. In theillustrative embodiment, to make sure that the system does notmistakenly interfere with the unintended receivers 310 (e.g., incumbentPtP communication system), if the terminal 410 controller requiresreliable direction reading (which in this scenarit does not have), itmay disable transmission, accordingly.

FIG. 30, in particular, illustrates an example procedure for magneticcompass confirmation, e.g., for avoidance of interference in wirelesscommunications in accordance with one or more embodiments describedherein. For example, one or more non-generic, specifically configureddevices (e.g., terminal 600) may perform procedure 3000 by executingstored instructions. Note that the procedure 3000 may be performed by adirectionally sensitive system (i.e., the process is on thesystem/terminal/device), or else may be performed by a controllingdevice (e.g., server) that has access to the parameters and control ofthe directionally sensitive system 2600.

As shown in FIG. 30, the procedure 3000 may start at step 3005, andcontinues to step 3010, where, as described in greater detail above, aprocess obtains a first compensated directional reading from a firstdirectional sensor 2610 of a directionally sensitive system 2600, and toobtain a second compensated directional reading from a seconddirectional sensor 2620 of the directionally sensitive system in step3015. As mentioned above, the first and second directional sensors maybe any suitable sensor, such as a magnetometer, an accelerometer, agyroscope, a GPS location sensor, and so on, as well as combinationsthereof (e.g., existing sophisticated compass algorithms may be based onnine-axis inputs (e.g., accelerometer, gyro and magnetometer)). In oneembodiment, the first and second directional sensors are located on asame device 2630, however, in another embodiment, they may be located ondifferent first and second devices (2640 and 2645), respectively, wherethe first and second devices are in communication with each other, asdescribed above. According to the techniques herein, the first andsecond sensors are meant to be affected by interference differently,such as by having a different compensated interference sensitivity fromeach other (e.g., different types of sensors), or, particularly whenbuilt based on the same technology, by having different locations withinthe directionally sensitive system than each other. (Note again that thesystem herein may first attempt to correct for the magnetic fielddistortion, and it is only after the system realizes that it is not ableto correct/compensate for the distortion that it determines aninaccurate reading, and illustratively in one embodiment, moves to thestate wherein if directional sensitivity is critical, it preventstransmission.)

In step 3020, the process determines a difference between the firstcompensated directional reading and the second compensated directionalreading. For example, by comparing the first and second compensatedbearing readings from the two sensors, the techniques herein candetermine whether the true north bearing is accurate based on whetherthe two readings are substantially the same. In particular, in step3025, the process may declare whether the directional reading isaccurate or inaccurate. That is, in response to the difference beinggreater than an acceptable threshold, the process can declare aninaccurate directional reading, while in response to there being nosubstantial difference between the first compensated directional readingand the second compensated directional reading, or in response to thedifference being less than or equal to the acceptable threshold, theprocess can declare an accurate directional reading. (Note that asdescribed above, embodiments herein may perform a “smearing” techniqueon protection zones—as such, in another embodiment herein, thetechniques herein may use the different compensated directional readingsto estimate an uncertainty/inaccuracy in the direction, and smear theprotection zone accordingly.)

Note that as described above, in response to the difference being lessthan or equal to an acceptable threshold (when this is an acceptableaccurate reading), an accurate directional reading can be determined asan average between the first and second directional readings. Forinstance, assume that one embodiment assigns a primary status to“Compass 1”, and a verification status to “Compass 2” (or 2 and 3). Oneoption is that if Compass 2 (or 2 and 3) agrees with Compass 1 within Xdegrees, the heading of Compass 1 may be used. In another option, ifCompass 1 and 2 agree within X degrees, the headings of Compass 1 and 2may be averaged. (In still another optional configuration, headingreadings may be obtained from Compass 1, Compass 2, and Compass 3—If allcompasses agree within X degrees, the headings of the two compasseswhose readings most closely align may be averaged.) Still otherembodiments and configurations may be made in accordance with thetechniques herein, and those specifically mentioned herein are not meantto be limiting to the scope of the present disclosure.

In step 3030, in response to an inaccurate directional reading, theprocess may prevent performance of a directionally sensitive action bythe directionally sensitive system. Alternatively, in step 3035, inresponse to the system determining that it was able to obtain anaccurate directional reading, the process may correspondingly enableperformance of the directionally sensitive action by the directionallysensitive system. As an illustrative and non-limiting example, thedirectionally sensitive action may comprise transmitting a transmission405 from the directionally sensitive system (terminal 410) toward anintended receiver 420 (e.g., satellite) at a direction that avoidshaving the transmission interfere with an unintended receiver 430 (e.g.,an earth-based PtPR). Said differently, in one specific embodiment, thetechniques herein may be configured to disable transmission from aterminal 410 when the system cannot guarantee that it can reliablytransmit towards the satellite 420 without interfering with incumbentPtPRs 430, based on determining the accuracy of various directionalfactors, as described above.

As noted above, compass heading and pitch are often calculated using“fusion algorithms” drawing data from multiple sensors. For instance,one specific (and non-limiting) example fusion algorithm that fusesinformation from multiple sensors is a “nine-axis” fusion algorithm,where multiple sensors (e.g., three) each provide data in threeorthogonal axes X, Y, and Z: 1) a magnetometer reading earth's magneticfield (e.g., in X, Y, and Z), 2) an accelerometer reading acceleration(e.g., in X, Y, and Z), and 3) a gyroscope reading change in direction(e.g., in X, Y, and Z). The fusion algorithms can thus provide moreaccurate heading than using a magnetometer alone. According to one ormore embodiments herein, therefore, one or both of the directionalreadings may be based on a fusion algorithm using input from a pluralityof directional sensors. As described below, the fusion algorithms may bedifferent, and/or at least one sensor may be different between the twosets of sensors (e.g., for the same or different fusion algorithms).

Specifically, in one embodiment, the techniques herein may read datafrom one set of sensors (e.g., accelerometer, gyro and a magnetometer)using one fusion algorithm to obtain a first compensating bearing, andreading the data from the same set of sensors using a different fusionalgorithm to obtain a second compensated bearing. By comparing the firstand second compensated bearing readings from the two fusion algorithms,the techniques herein can determining that the true north bearing isaccurate when the two readings are substantially the same (aftercompensation) or erroneous when the two readings are substantiallydifferent, and may correspondingly enable or block an action (e.g.,terminal transmission or otherwise) based on the accuracy (e.g., whenaccuracy is required).

In another specific embodiment, the techniques herein may read data fromone set of sensors (e.g., accelerometer, gyro and a magnetometer) usingone fusion algorithm to obtain the first bearing, and then may read thedata from the same gyro and accelerometer, but with a differentmagnetometer. Either the same fusion algorithm or a different fusionalgorithm may be used to obtain the second bearing, and after comparingthe first and second bearing readings, the system can enable or preventthe action, accordingly. Other combinations of sets of sensors may beread as the different readings, such as, for example:

-   -   the same accelerometer, and different gyros and magnetometers;        or    -   the same gyro, and different accelerometers and magnetometers;        or    -   different accelerometers, gyros, and magnetometers.

Note that still further specific embodiments allow for the firstdirectional readings to be based on a measured magnetic property value(e.g., a measured magnetic field strength or dip angle), where thesecond directional reading is then an “expected” magnetic property value(e.g., magnetic field strength or dip angle, respectively) based on ageographic location of the directionally sensitive system as determinedby the second directional sensor. That is, the techniques herein providefor reading magnetic field strength (or dip angle) and GPS location,comparing it to published data of expected magnetic field strength (ordip angle) at the GPS location. If the two readings are substantiallythe same, then the direction (true north bearing) of the directionalsensor may be declared accurate, while if they are different, then aninaccuracy can be assumed.

The illustrative procedure 3000 may end in step 3040, notably with theoption to receive updated readings and to perform further comparisons(e.g., in response to moving the system away from interference). Thatis, though the process in FIG. 30 shows an ending at step 3040, theprocess may take place continuously, and as such as the process ends instep 3040, it immediately starts anew in step 3005 (i.e., an infiniteloop wherein the process continuously assesses the confidence of itsbearing accuracy).

It should be noted that while certain steps within procedure 3000 may beoptional as described above, the steps shown in FIG. 30 are merelyexamples for illustration, and certain other steps may be included orexcluded as desired. Further, while a particular order of the steps isshown, this ordering is merely illustrative, and any suitablearrangement of the steps may be utilized without departing from thescope of the embodiments herein. Moreover, while procedures 1200 (fromFIGS. 12A-12B above) and 3000 are described separately, certain stepsfrom each procedure may be incorporated into each other procedure, andthe procedures are not meant to be mutually exclusive.

Advantageously, the techniques herein provide for magnetic compassconfirmation, or, more particularly, directional sensor confirmation. Inone embodiment, the techniques herein specifically avoid of interferencein wireless communications whenever there is doubt about a criticaldirectional reading. Other applications that require criticaldirectional/compass reading confirmation may also make use of thetechniques described herein.

While there have been shown and described illustrative embodiments thatrelate to interference management techniques in wireless communicationnetworks, it is to be understood that various other adaptations andmodifications may be made within the scope of the embodiments herein.For example, the embodiments may, in fact, be used in a variety of typesof wireless communication networks and/or protocols, and need not belimited to the illustrative satellite network implementation, PtPnetworks, or even communication in the C-band. For example, though thedisclosure was described with respect to satellite communication in theC-Band, those skilled in the art should understand that this was doneonly for illustrative purpose and without limitations. The techniquesherein, in particular, are applicable to any other communication bandsuch as the Ku-band (e.g., Downlink: 11.7-12.2 GHz; Uplink: 14.0-14.5GHz) or any other suitable band. Furthermore, while the embodiments mayhave been demonstrated with respect to certain communicationenvironments, physical environments, or device form factors, otherconfigurations may be conceived by those skilled in the art that wouldremain within the contemplated subject matter of the description above.

Additionally, while certain configurations of terminals and receiversare shown (e.g., PtPRs and satellites), it is important to note thatunintended receivers may actually be a part of the same communicationnetwork as the intended receiver, or at least the same type of device.For instance, an intended receiver could be a first satellite, and anunintended receiver may be a second satellite, which may be in the samenetwork as the first satellite (e.g., preventing double reception of thesame message), or else may be in a different network (e.g., a differentsatellite communication network that uses the same channels). In stillother embodiments, one network may be based on geostationary orbit (GEO)satellites and the other network may be based on low earth orbit (LEO)satellites, or else both may be based on GEO or both based on LEO. Othermobile communication techniques may also be used, such as those based onland or carried by UAVs or other flying vehicles. Further, it is alsoimportant to note that in the case of drones or UAVs, a portion of thecommunication parameters takes into consideration elevation above sealevel, such as raising or lowering the drone to change the link-budgetcalculations or line-of-sight determinations detailed above.

In particular, the foregoing description has been directed to specificembodiments. It will be apparent, however, that other variations andmodifications may be made to the described embodiments, with theattainment of some or all of their advantages. For instance, it isexpressly contemplated that certain components and/or elements describedherein can be implemented as software being stored on a tangible(non-transitory) computer-readable medium (e.g.,disks/CDs/RAM/EEPROM/etc.) having program instructions executing on acomputer, hardware, firmware, or a combination thereof. Accordingly thisdescription is to be taken only by way of example and not to otherwiselimit the scope of the embodiments herein. Therefore, it is the objectof the appended claims to cover all such variations and modifications ascome within the true spirit and scope of the embodiments herein.

What is claimed is:
 1. A method, comprising: obtaining, by a process, afirst compensated directional reading from a first directional sensor ofa directionally sensitive system; obtaining, by the process, a secondcompensated directional reading from a second directional sensor of thedirectionally sensitive system; determining, by the process, adifference between the first compensated directional reading and thesecond compensated directional reading; declaring, by the process inresponse to the difference being greater than an acceptable threshold,an inaccurate directional reading; and preventing, by the process,performance of a directionally sensitive action by the directionallysensitive system in response to an inaccurate directional reading. 2.The method as in claim 1, further comprising: enabling performance ofthe directionally sensitive action by the directionally sensitive systemin response to an accurate directional reading.
 3. The method as inclaim 1, wherein the directionally sensitive action comprisestransmitting a transmission from the directionally sensitive systemtoward an intended receiver at a direction that avoids having thetransmission interfere with an unintended receiver.
 4. The method as inclaim 3, wherein the intended receiver is a satellite receiver, andwherein the unintended receiver is one of either an earth-basedpoint-to-point receiver (PtPR) or another satellite receiver.
 5. Themethod as in claim 1, wherein the first and second directional sensorsare located on a same device.
 6. The method as in claim 1, wherein thefirst and second directional sensors are located on different first andsecond devices, respectively, wherein the first and second devices arein communication with each other.
 7. The method as in claim 1, whereinthe first directional sensor has a different interference sensitivitythan the second directional sensor.
 8. The method as in claim 1, furthercomprising: declaring, in response to the difference being less than orequal to the acceptable threshold, an accurate directional reading. 9.The method as in claim 8, further comprising: determining, in responseto the difference being less than or equal to the acceptable threshold,an accurate directional reading as an average between the first andsecond directional readings.
 10. The method as in claim 1, wherein thefirst directional reading is based on a first fusion algorithm usinginput from a first plurality of directional sensors, and wherein thesecond directional reading is based on a second fusion algorithm usinginput from a second plurality of directional sensors.
 11. The method asin claim 10, wherein at least one sensor from the second plurality ofdirectional sensors is not within the first plurality of directionalsensors.
 12. The method as in claim 1, wherein the first directionalreading is a measured magnetic property value, and wherein the seconddirectional reading is an expected magnetic property value based on ageographic location of the directionally sensitive system as determinedby the second directional sensor.
 13. The method as in claim 1, furthercomprising: determining, based on the difference between the firstcompensated directional reading and the second compensated directionalreading, an estimated inaccuracy in the directional reading; andsmearing, based on the estimated inaccuracy in the directional reading,one or more protection zones which define locations where adirectionally sensitive transmission might interfere with an unintendedreceiver.
 14. An apparatus, comprising: one or more communicationinterfaces; a processor coupled to the interfaces and adapted to executeone or more processes; and a memory configured to store a processexecutable by the processor, the process when executed operable to:obtain a first compensated directional reading from a first directionalsensor of a directionally sensitive system; obtain a second compensateddirectional reading from a second directional sensor of thedirectionally sensitive system; determine a difference between the firstcompensated directional reading and the second compensated directionalreading; declare, in response to the difference being greater than anacceptable threshold, an inaccurate directional reading; and preventperformance of a directionally sensitive action by the directionallysensitive system in response to an inaccurate directional reading. 15.The apparatus as in claim 14, wherein the directionally sensitive actioncomprises transmitting a transmission from the directionally sensitivesystem toward an intended receiver at a direction that avoids having thetransmission interfere with an unintended receiver.
 16. The apparatus asin claim 14, wherein the first and second directional sensors arelocated on a same device.
 17. The apparatus as in claim 14, wherein thefirst and second directional sensors are located on different first andsecond devices, respectively, wherein the first and second devices arein communication with each other.
 18. The apparatus as in claim 14,wherein the first directional sensor has a different interferencesensitivity than the second directional sensor.
 19. The apparatus as inclaim 14, wherein the process when executed is further operable to:declare, in response to the difference being less than or equal to theacceptable threshold, an accurate directional reading.
 20. The apparatusas in claim 14, wherein the first directional reading is based on afirst fusion algorithm using input from a first plurality of directionalsensors, and wherein the second directional reading is based on a secondfusion algorithm using input from a second plurality of directionalsensors.
 21. The apparatus as in claim 20, wherein at least one sensorfrom the second plurality of directional sensors is not within the firstplurality of directional sensors.
 22. The apparatus as in claim 14,wherein the first directional reading is a measured magnetic propertyvalue, and wherein the second directional reading is an expectedmagnetic property value based on a geographic location of thedirectionally sensitive system as determined by the second directionalsensor.
 23. The apparatus as in claim 14, wherein the apparatus is thedirectionally sensitive system.
 24. A tangible, non-transitory,computer-readable medium having computer-executable instructions storedthereon that, when executed by a processor on a computer, cause thecomputer to perform a method comprising: obtaining a first compensateddirectional reading from a first directional sensor of a directionallysensitive system; obtaining a second compensated directional readingfrom a second directional sensor of the directionally sensitive system;determining a difference between the first compensated directionalreading and the second compensated directional reading; declaring, inresponse to the difference being greater than an acceptable threshold,an inaccurate directional reading; and preventing performance of adirectionally sensitive action by the directionally sensitive system inresponse to an inaccurate directional reading.